fix: prevent server hang and output corruption in spawn handling (#23)

- Add process 'error' event handler to catch spawn failures (e.g., yt-dlp not installed)
- Separate stdout/stderr to prevent yt-dlp warnings from corrupting parsed output
- Add try-catch for RegExp construction from YTDLP_SANITIZE_ILLEGAL_CHARS env var
- Add NaN validation for YTDLP_MAX_FILENAME_LENGTH env var
- Sync VERSION constant with package.json (0.8.4)
- Update tests for new output format and null handling
- Add version sync guidance to CLAUDE.md

.claude/skills/mcp-builder/LICENSE.txt

@@ -0,0 +1,202 @@
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.claude/skills/mcp-builder/SKILL.md

@@ -0,0 +1,328 @@
+---
+name: mcp-builder
+description: Guide for creating high-quality MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript (MCP SDK).
+license: Complete terms in LICENSE.txt
+---
+
+# MCP Server Development Guide
+
+## Overview
+
+To create high-quality MCP (Model Context Protocol) servers that enable LLMs to effectively interact with external services, use this skill. An MCP server provides tools that allow LLMs to access external services and APIs. The quality of an MCP server is measured by how well it enables LLMs to accomplish real-world tasks using the tools provided.
+
+---
+
+# Process
+
+## 🚀 High-Level Workflow
+
+Creating a high-quality MCP server involves four main phases:
+
+### Phase 1: Deep Research and Planning
+
+#### 1.1 Understand Agent-Centric Design Principles
+
+Before diving into implementation, understand how to design tools for AI agents by reviewing these principles:
+
+**Build for Workflows, Not Just API Endpoints:**
+- Don't simply wrap existing API endpoints - build thoughtful, high-impact workflow tools
+- Consolidate related operations (e.g., `schedule_event` that both checks availability and creates event)
+- Focus on tools that enable complete tasks, not just individual API calls
+- Consider what workflows agents actually need to accomplish
+
+**Optimize for Limited Context:**
+- Agents have constrained context windows - make every token count
+- Return high-signal information, not exhaustive data dumps
+- Provide "concise" vs "detailed" response format options
+- Default to human-readable identifiers over technical codes (names over IDs)
+- Consider the agent's context budget as a scarce resource
+
+**Design Actionable Error Messages:**
+- Error messages should guide agents toward correct usage patterns
+- Suggest specific next steps: "Try using filter='active_only' to reduce results"
+- Make errors educational, not just diagnostic
+- Help agents learn proper tool usage through clear feedback
+
+**Follow Natural Task Subdivisions:**
+- Tool names should reflect how humans think about tasks
+- Group related tools with consistent prefixes for discoverability
+- Design tools around natural workflows, not just API structure
+
+**Use Evaluation-Driven Development:**
+- Create realistic evaluation scenarios early
+- Let agent feedback drive tool improvements
+- Prototype quickly and iterate based on actual agent performance
+
+#### 1.3 Study MCP Protocol Documentation
+
+**Fetch the latest MCP protocol documentation:**
+
+Use WebFetch to load: `https://modelcontextprotocol.io/llms-full.txt`
+
+This comprehensive document contains the complete MCP specification and guidelines.
+
+#### 1.4 Study Framework Documentation
+
+**Load and read the following reference files:**
+
+- **MCP Best Practices**: [📋 View Best Practices](./reference/mcp_best_practices.md) - Core guidelines for all MCP servers
+
+**For Python implementations, also load:**
+- **Python SDK Documentation**: Use WebFetch to load `https://raw.githubusercontent.com/modelcontextprotocol/python-sdk/main/README.md`
+- [🐍 Python Implementation Guide](./reference/python_mcp_server.md) - Python-specific best practices and examples
+
+**For Node/TypeScript implementations, also load:**
+- **TypeScript SDK Documentation**: Use WebFetch to load `https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/main/README.md`
+- [⚡ TypeScript Implementation Guide](./reference/node_mcp_server.md) - Node/TypeScript-specific best practices and examples
+
+#### 1.5 Exhaustively Study API Documentation
+
+To integrate a service, read through **ALL** available API documentation:
+- Official API reference documentation
+- Authentication and authorization requirements
+- Rate limiting and pagination patterns
+- Error responses and status codes
+- Available endpoints and their parameters
+- Data models and schemas
+
+**To gather comprehensive information, use web search and the WebFetch tool as needed.**
+
+#### 1.6 Create a Comprehensive Implementation Plan
+
+Based on your research, create a detailed plan that includes:
+
+**Tool Selection:**
+- List the most valuable endpoints/operations to implement
+- Prioritize tools that enable the most common and important use cases
+- Consider which tools work together to enable complex workflows
+
+**Shared Utilities and Helpers:**
+- Identify common API request patterns
+- Plan pagination helpers
+- Design filtering and formatting utilities
+- Plan error handling strategies
+
+**Input/Output Design:**
+- Define input validation models (Pydantic for Python, Zod for TypeScript)
+- Design consistent response formats (e.g., JSON or Markdown), and configurable levels of detail (e.g., Detailed or Concise)
+- Plan for large-scale usage (thousands of users/resources)
+- Implement character limits and truncation strategies (e.g., 25,000 tokens)
+
+**Error Handling Strategy:**
+- Plan graceful failure modes
+- Design clear, actionable, LLM-friendly, natural language error messages which prompt further action
+- Consider rate limiting and timeout scenarios
+- Handle authentication and authorization errors
+
+---
+
+### Phase 2: Implementation
+
+Now that you have a comprehensive plan, begin implementation following language-specific best practices.
+
+#### 2.1 Set Up Project Structure
+
+**For Python:**
+- Create a single `.py` file or organize into modules if complex (see [🐍 Python Guide](./reference/python_mcp_server.md))
+- Use the MCP Python SDK for tool registration
+- Define Pydantic models for input validation
+
+**For Node/TypeScript:**
+- Create proper project structure (see [⚡ TypeScript Guide](./reference/node_mcp_server.md))
+- Set up `package.json` and `tsconfig.json`
+- Use MCP TypeScript SDK
+- Define Zod schemas for input validation
+
+#### 2.2 Implement Core Infrastructure First
+
+**To begin implementation, create shared utilities before implementing tools:**
+- API request helper functions
+- Error handling utilities
+- Response formatting functions (JSON and Markdown)
+- Pagination helpers
+- Authentication/token management
+
+#### 2.3 Implement Tools Systematically
+
+For each tool in the plan:
+
+**Define Input Schema:**
+- Use Pydantic (Python) or Zod (TypeScript) for validation
+- Include proper constraints (min/max length, regex patterns, min/max values, ranges)
+- Provide clear, descriptive field descriptions
+- Include diverse examples in field descriptions
+
+**Write Comprehensive Docstrings/Descriptions:**
+- One-line summary of what the tool does
+- Detailed explanation of purpose and functionality
+- Explicit parameter types with examples
+- Complete return type schema
+- Usage examples (when to use, when not to use)
+- Error handling documentation, which outlines how to proceed given specific errors
+
+**Implement Tool Logic:**
+- Use shared utilities to avoid code duplication
+- Follow async/await patterns for all I/O
+- Implement proper error handling
+- Support multiple response formats (JSON and Markdown)
+- Respect pagination parameters
+- Check character limits and truncate appropriately
+
+**Add Tool Annotations:**
+- `readOnlyHint`: true (for read-only operations)
+- `destructiveHint`: false (for non-destructive operations)
+- `idempotentHint`: true (if repeated calls have same effect)
+- `openWorldHint`: true (if interacting with external systems)
+
+#### 2.4 Follow Language-Specific Best Practices
+
+**At this point, load the appropriate language guide:**
+
+**For Python: Load [🐍 Python Implementation Guide](./reference/python_mcp_server.md) and ensure the following:**
+- Using MCP Python SDK with proper tool registration
+- Pydantic v2 models with `model_config`
+- Type hints throughout
+- Async/await for all I/O operations
+- Proper imports organization
+- Module-level constants (CHARACTER_LIMIT, API_BASE_URL)
+
+**For Node/TypeScript: Load [⚡ TypeScript Implementation Guide](./reference/node_mcp_server.md) and ensure the following:**
+- Using `server.registerTool` properly
+- Zod schemas with `.strict()`
+- TypeScript strict mode enabled
+- No `any` types - use proper types
+- Explicit Promise<T> return types
+- Build process configured (`npm run build`)
+
+---
+
+### Phase 3: Review and Refine
+
+After initial implementation:
+
+#### 3.1 Code Quality Review
+
+To ensure quality, review the code for:
+- **DRY Principle**: No duplicated code between tools
+- **Composability**: Shared logic extracted into functions
+- **Consistency**: Similar operations return similar formats
+- **Error Handling**: All external calls have error handling
+- **Type Safety**: Full type coverage (Python type hints, TypeScript types)
+- **Documentation**: Every tool has comprehensive docstrings/descriptions
+
+#### 3.2 Test and Build
+
+**Important:** MCP servers are long-running processes that wait for requests over stdio/stdin or sse/http. Running them directly in your main process (e.g., `python server.py` or `node dist/index.js`) will cause your process to hang indefinitely.
+
+**Safe ways to test the server:**
+- Use the evaluation harness (see Phase 4) - recommended approach
+- Run the server in tmux to keep it outside your main process
+- Use a timeout when testing: `timeout 5s python server.py`
+
+**For Python:**
+- Verify Python syntax: `python -m py_compile your_server.py`
+- Check imports work correctly by reviewing the file
+- To manually test: Run server in tmux, then test with evaluation harness in main process
+- Or use the evaluation harness directly (it manages the server for stdio transport)
+
+**For Node/TypeScript:**
+- Run `npm run build` and ensure it completes without errors
+- Verify dist/index.js is created
+- To manually test: Run server in tmux, then test with evaluation harness in main process
+- Or use the evaluation harness directly (it manages the server for stdio transport)
+
+#### 3.3 Use Quality Checklist
+
+To verify implementation quality, load the appropriate checklist from the language-specific guide:
+- Python: see "Quality Checklist" in [🐍 Python Guide](./reference/python_mcp_server.md)
+- Node/TypeScript: see "Quality Checklist" in [⚡ TypeScript Guide](./reference/node_mcp_server.md)
+
+---
+
+### Phase 4: Create Evaluations
+
+After implementing your MCP server, create comprehensive evaluations to test its effectiveness.
+
+**Load [✅ Evaluation Guide](./reference/evaluation.md) for complete evaluation guidelines.**
+
+#### 4.1 Understand Evaluation Purpose
+
+Evaluations test whether LLMs can effectively use your MCP server to answer realistic, complex questions.
+
+#### 4.2 Create 10 Evaluation Questions
+
+To create effective evaluations, follow the process outlined in the evaluation guide:
+
+1. **Tool Inspection**: List available tools and understand their capabilities
+2. **Content Exploration**: Use READ-ONLY operations to explore available data
+3. **Question Generation**: Create 10 complex, realistic questions
+4. **Answer Verification**: Solve each question yourself to verify answers
+
+#### 4.3 Evaluation Requirements
+
+Each question must be:
+- **Independent**: Not dependent on other questions
+- **Read-only**: Only non-destructive operations required
+- **Complex**: Requiring multiple tool calls and deep exploration
+- **Realistic**: Based on real use cases humans would care about
+- **Verifiable**: Single, clear answer that can be verified by string comparison
+- **Stable**: Answer won't change over time
+
+#### 4.4 Output Format
+
+Create an XML file with this structure:
+
+```xml
+<evaluation>
+  <qa_pair>
+    <question>Find discussions about AI model launches with animal codenames. One model needed a specific safety designation that uses the format ASL-X. What number X was being determined for the model named after a spotted wild cat?</question>
+    <answer>3</answer>
+  </qa_pair>
+<!-- More qa_pairs... -->
+</evaluation>
+```
+
+---
+
+# Reference Files
+
+## 📚 Documentation Library
+
+Load these resources as needed during development:
+
+### Core MCP Documentation (Load First)
+- **MCP Protocol**: Fetch from `https://modelcontextprotocol.io/llms-full.txt` - Complete MCP specification
+- [📋 MCP Best Practices](./reference/mcp_best_practices.md) - Universal MCP guidelines including:
+  - Server and tool naming conventions
+  - Response format guidelines (JSON vs Markdown)
+  - Pagination best practices
+  - Character limits and truncation strategies
+  - Tool development guidelines
+  - Security and error handling standards
+
+### SDK Documentation (Load During Phase 1/2)
+- **Python SDK**: Fetch from `https://raw.githubusercontent.com/modelcontextprotocol/python-sdk/main/README.md`
+- **TypeScript SDK**: Fetch from `https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/main/README.md`
+
+### Language-Specific Implementation Guides (Load During Phase 2)
+- [🐍 Python Implementation Guide](./reference/python_mcp_server.md) - Complete Python/FastMCP guide with:
+  - Server initialization patterns
+  - Pydantic model examples
+  - Tool registration with `@mcp.tool`
+  - Complete working examples
+  - Quality checklist
+
+- [⚡ TypeScript Implementation Guide](./reference/node_mcp_server.md) - Complete TypeScript guide with:
+  - Project structure
+  - Zod schema patterns
+  - Tool registration with `server.registerTool`
+  - Complete working examples
+  - Quality checklist
+
+### Evaluation Guide (Load During Phase 4)
+- [✅ Evaluation Guide](./reference/evaluation.md) - Complete evaluation creation guide with:
+  - Question creation guidelines
+  - Answer verification strategies
+  - XML format specifications
+  - Example questions and answers
+  - Running an evaluation with the provided scripts

.claude/skills/mcp-builder/scripts/connections.py

@@ -0,0 +1,151 @@
+"""Lightweight connection handling for MCP servers."""
+
+from abc import ABC, abstractmethod
+from contextlib import AsyncExitStack
+from typing import Any
+
+from mcp import ClientSession, StdioServerParameters
+from mcp.client.sse import sse_client
+from mcp.client.stdio import stdio_client
+from mcp.client.streamable_http import streamablehttp_client
+
+
+class MCPConnection(ABC):
+    """Base class for MCP server connections."""
+
+    def __init__(self):
+        self.session = None
+        self._stack = None
+
+    @abstractmethod
+    def _create_context(self):
+        """Create the connection context based on connection type."""
+
+    async def __aenter__(self):
+        """Initialize MCP server connection."""
+        self._stack = AsyncExitStack()
+        await self._stack.__aenter__()
+
+        try:
+            ctx = self._create_context()
+            result = await self._stack.enter_async_context(ctx)
+
+            if len(result) == 2:
+                read, write = result
+            elif len(result) == 3:
+                read, write, _ = result
+            else:
+                raise ValueError(f"Unexpected context result: {result}")
+
+            session_ctx = ClientSession(read, write)
+            self.session = await self._stack.enter_async_context(session_ctx)
+            await self.session.initialize()
+            return self
+        except BaseException:
+            await self._stack.__aexit__(None, None, None)
+            raise
+
+    async def __aexit__(self, exc_type, exc_val, exc_tb):
+        """Clean up MCP server connection resources."""
+        if self._stack:
+            await self._stack.__aexit__(exc_type, exc_val, exc_tb)
+        self.session = None
+        self._stack = None
+
+    async def list_tools(self) -> list[dict[str, Any]]:
+        """Retrieve available tools from the MCP server."""
+        response = await self.session.list_tools()
+        return [
+            {
+                "name": tool.name,
+                "description": tool.description,
+                "input_schema": tool.inputSchema,
+            }
+            for tool in response.tools
+        ]
+
+    async def call_tool(self, tool_name: str, arguments: dict[str, Any]) -> Any:
+        """Call a tool on the MCP server with provided arguments."""
+        result = await self.session.call_tool(tool_name, arguments=arguments)
+        return result.content
+
+
+class MCPConnectionStdio(MCPConnection):
+    """MCP connection using standard input/output."""
+
+    def __init__(self, command: str, args: list[str] = None, env: dict[str, str] = None):
+        super().__init__()
+        self.command = command
+        self.args = args or []
+        self.env = env
+
+    def _create_context(self):
+        return stdio_client(
+            StdioServerParameters(command=self.command, args=self.args, env=self.env)
+        )
+
+
+class MCPConnectionSSE(MCPConnection):
+    """MCP connection using Server-Sent Events."""
+
+    def __init__(self, url: str, headers: dict[str, str] = None):
+        super().__init__()
+        self.url = url
+        self.headers = headers or {}
+
+    def _create_context(self):
+        return sse_client(url=self.url, headers=self.headers)
+
+
+class MCPConnectionHTTP(MCPConnection):
+    """MCP connection using Streamable HTTP."""
+
+    def __init__(self, url: str, headers: dict[str, str] = None):
+        super().__init__()
+        self.url = url
+        self.headers = headers or {}
+
+    def _create_context(self):
+        return streamablehttp_client(url=self.url, headers=self.headers)
+
+
+def create_connection(
+    transport: str,
+    command: str = None,
+    args: list[str] = None,
+    env: dict[str, str] = None,
+    url: str = None,
+    headers: dict[str, str] = None,
+) -> MCPConnection:
+    """Factory function to create the appropriate MCP connection.
+
+    Args:
+        transport: Connection type ("stdio", "sse", or "http")
+        command: Command to run (stdio only)
+        args: Command arguments (stdio only)
+        env: Environment variables (stdio only)
+        url: Server URL (sse and http only)
+        headers: HTTP headers (sse and http only)
+
+    Returns:
+        MCPConnection instance
+    """
+    transport = transport.lower()
+
+    if transport == "stdio":
+        if not command:
+            raise ValueError("Command is required for stdio transport")
+        return MCPConnectionStdio(command=command, args=args, env=env)
+
+    elif transport == "sse":
+        if not url:
+            raise ValueError("URL is required for sse transport")
+        return MCPConnectionSSE(url=url, headers=headers)
+
+    elif transport in ["http", "streamable_http", "streamable-http"]:
+        if not url:
+            raise ValueError("URL is required for http transport")
+        return MCPConnectionHTTP(url=url, headers=headers)
+
+    else:
+        raise ValueError(f"Unsupported transport type: {transport}. Use 'stdio', 'sse', or 'http'")

.claude/skills/mcp-builder/scripts/evaluation.py

@@ -0,0 +1,373 @@
+"""MCP Server Evaluation Harness
+
+This script evaluates MCP servers by running test questions against them using Claude.
+"""
+
+import argparse
+import asyncio
+import json
+import re
+import sys
+import time
+import traceback
+import xml.etree.ElementTree as ET
+from pathlib import Path
+from typing import Any
+
+from anthropic import Anthropic
+
+from connections import create_connection
+
+EVALUATION_PROMPT = """You are an AI assistant with access to tools.
+
+When given a task, you MUST:
+1. Use the available tools to complete the task
+2. Provide summary of each step in your approach, wrapped in <summary> tags
+3. Provide feedback on the tools provided, wrapped in <feedback> tags
+4. Provide your final response, wrapped in <response> tags
+
+Summary Requirements:
+- In your <summary> tags, you must explain:
+  - The steps you took to complete the task
+  - Which tools you used, in what order, and why
+  - The inputs you provided to each tool
+  - The outputs you received from each tool
+  - A summary for how you arrived at the response
+
+Feedback Requirements:
+- In your <feedback> tags, provide constructive feedback on the tools:
+  - Comment on tool names: Are they clear and descriptive?
+  - Comment on input parameters: Are they well-documented? Are required vs optional parameters clear?
+  - Comment on descriptions: Do they accurately describe what the tool does?
+  - Comment on any errors encountered during tool usage: Did the tool fail to execute? Did the tool return too many tokens?
+  - Identify specific areas for improvement and explain WHY they would help
+  - Be specific and actionable in your suggestions
+
+Response Requirements:
+- Your response should be concise and directly address what was asked
+- Always wrap your final response in <response> tags
+- If you cannot solve the task return <response>NOT_FOUND</response>
+- For numeric responses, provide just the number
+- For IDs, provide just the ID
+- For names or text, provide the exact text requested
+- Your response should go last"""
+
+
+def parse_evaluation_file(file_path: Path) -> list[dict[str, Any]]:
+    """Parse XML evaluation file with qa_pair elements."""
+    try:
+        tree = ET.parse(file_path)
+        root = tree.getroot()
+        evaluations = []
+
+        for qa_pair in root.findall(".//qa_pair"):
+            question_elem = qa_pair.find("question")
+            answer_elem = qa_pair.find("answer")
+
+            if question_elem is not None and answer_elem is not None:
+                evaluations.append({
+                    "question": (question_elem.text or "").strip(),
+                    "answer": (answer_elem.text or "").strip(),
+                })
+
+        return evaluations
+    except Exception as e:
+        print(f"Error parsing evaluation file {file_path}: {e}")
+        return []
+
+
+def extract_xml_content(text: str, tag: str) -> str | None:
+    """Extract content from XML tags."""
+    pattern = rf"<{tag}>(.*?)</{tag}>"
+    matches = re.findall(pattern, text, re.DOTALL)
+    return matches[-1].strip() if matches else None
+
+
+async def agent_loop(
+    client: Anthropic,
+    model: str,
+    question: str,
+    tools: list[dict[str, Any]],
+    connection: Any,
+) -> tuple[str, dict[str, Any]]:
+    """Run the agent loop with MCP tools."""
+    messages = [{"role": "user", "content": question}]
+
+    response = await asyncio.to_thread(
+        client.messages.create,
+        model=model,
+        max_tokens=4096,
+        system=EVALUATION_PROMPT,
+        messages=messages,
+        tools=tools,
+    )
+
+    messages.append({"role": "assistant", "content": response.content})
+
+    tool_metrics = {}
+
+    while response.stop_reason == "tool_use":
+        tool_use = next(block for block in response.content if block.type == "tool_use")
+        tool_name = tool_use.name
+        tool_input = tool_use.input
+
+        tool_start_ts = time.time()
+        try:
+            tool_result = await connection.call_tool(tool_name, tool_input)
+            tool_response = json.dumps(tool_result) if isinstance(tool_result, (dict, list)) else str(tool_result)
+        except Exception as e:
+            tool_response = f"Error executing tool {tool_name}: {str(e)}\n"
+            tool_response += traceback.format_exc()
+        tool_duration = time.time() - tool_start_ts
+
+        if tool_name not in tool_metrics:
+            tool_metrics[tool_name] = {"count": 0, "durations": []}
+        tool_metrics[tool_name]["count"] += 1
+        tool_metrics[tool_name]["durations"].append(tool_duration)
+
+        messages.append({
+            "role": "user",
+            "content": [{
+                "type": "tool_result",
+                "tool_use_id": tool_use.id,
+                "content": tool_response,
+            }]
+        })
+
+        response = await asyncio.to_thread(
+            client.messages.create,
+            model=model,
+            max_tokens=4096,
+            system=EVALUATION_PROMPT,
+            messages=messages,
+            tools=tools,
+        )
+        messages.append({"role": "assistant", "content": response.content})
+
+    response_text = next(
+        (block.text for block in response.content if hasattr(block, "text")),
+        None,
+    )
+    return response_text, tool_metrics
+
+
+async def evaluate_single_task(
+    client: Anthropic,
+    model: str,
+    qa_pair: dict[str, Any],
+    tools: list[dict[str, Any]],
+    connection: Any,
+    task_index: int,
+) -> dict[str, Any]:
+    """Evaluate a single QA pair with the given tools."""
+    start_time = time.time()
+
+    print(f"Task {task_index + 1}: Running task with question: {qa_pair['question']}")
+    response, tool_metrics = await agent_loop(client, model, qa_pair["question"], tools, connection)
+
+    response_value = extract_xml_content(response, "response")
+    summary = extract_xml_content(response, "summary")
+    feedback = extract_xml_content(response, "feedback")
+
+    duration_seconds = time.time() - start_time
+
+    return {
+        "question": qa_pair["question"],
+        "expected": qa_pair["answer"],
+        "actual": response_value,
+        "score": int(response_value == qa_pair["answer"]) if response_value else 0,
+        "total_duration": duration_seconds,
+        "tool_calls": tool_metrics,
+        "num_tool_calls": sum(len(metrics["durations"]) for metrics in tool_metrics.values()),
+        "summary": summary,
+        "feedback": feedback,
+    }
+
+
+REPORT_HEADER = """
+# Evaluation Report
+
+## Summary
+
+- **Accuracy**: {correct}/{total} ({accuracy:.1f}%)
+- **Average Task Duration**: {average_duration_s:.2f}s
+- **Average Tool Calls per Task**: {average_tool_calls:.2f}
+- **Total Tool Calls**: {total_tool_calls}
+
+---
+"""
+
+TASK_TEMPLATE = """
+### Task {task_num}
+
+**Question**: {question}
+**Ground Truth Answer**: `{expected_answer}`
+**Actual Answer**: `{actual_answer}`
+**Correct**: {correct_indicator}
+**Duration**: {total_duration:.2f}s
+**Tool Calls**: {tool_calls}
+
+**Summary**
+{summary}
+
+**Feedback**
+{feedback}
+
+---
+"""
+
+
+async def run_evaluation(
+    eval_path: Path,
+    connection: Any,
+    model: str = "claude-3-7-sonnet-20250219",
+) -> str:
+    """Run evaluation with MCP server tools."""
+    print("🚀 Starting Evaluation")
+
+    client = Anthropic()
+
+    tools = await connection.list_tools()
+    print(f"📋 Loaded {len(tools)} tools from MCP server")
+
+    qa_pairs = parse_evaluation_file(eval_path)
+    print(f"📋 Loaded {len(qa_pairs)} evaluation tasks")
+
+    results = []
+    for i, qa_pair in enumerate(qa_pairs):
+        print(f"Processing task {i + 1}/{len(qa_pairs)}")
+        result = await evaluate_single_task(client, model, qa_pair, tools, connection, i)
+        results.append(result)
+
+    correct = sum(r["score"] for r in results)
+    accuracy = (correct / len(results)) * 100 if results else 0
+    average_duration_s = sum(r["total_duration"] for r in results) / len(results) if results else 0
+    average_tool_calls = sum(r["num_tool_calls"] for r in results) / len(results) if results else 0
+    total_tool_calls = sum(r["num_tool_calls"] for r in results)
+
+    report = REPORT_HEADER.format(
+        correct=correct,
+        total=len(results),
+        accuracy=accuracy,
+        average_duration_s=average_duration_s,
+        average_tool_calls=average_tool_calls,
+        total_tool_calls=total_tool_calls,
+    )
+
+    report += "".join([
+        TASK_TEMPLATE.format(
+            task_num=i + 1,
+            question=qa_pair["question"],
+            expected_answer=qa_pair["answer"],
+            actual_answer=result["actual"] or "N/A",
+            correct_indicator="✅" if result["score"] else "❌",
+            total_duration=result["total_duration"],
+            tool_calls=json.dumps(result["tool_calls"], indent=2),
+            summary=result["summary"] or "N/A",
+            feedback=result["feedback"] or "N/A",
+        )
+        for i, (qa_pair, result) in enumerate(zip(qa_pairs, results))
+    ])
+
+    return report
+
+
+def parse_headers(header_list: list[str]) -> dict[str, str]:
+    """Parse header strings in format 'Key: Value' into a dictionary."""
+    headers = {}
+    if not header_list:
+        return headers
+
+    for header in header_list:
+        if ":" in header:
+            key, value = header.split(":", 1)
+            headers[key.strip()] = value.strip()
+        else:
+            print(f"Warning: Ignoring malformed header: {header}")
+    return headers
+
+
+def parse_env_vars(env_list: list[str]) -> dict[str, str]:
+    """Parse environment variable strings in format 'KEY=VALUE' into a dictionary."""
+    env = {}
+    if not env_list:
+        return env
+
+    for env_var in env_list:
+        if "=" in env_var:
+            key, value = env_var.split("=", 1)
+            env[key.strip()] = value.strip()
+        else:
+            print(f"Warning: Ignoring malformed environment variable: {env_var}")
+    return env
+
+
+async def main():
+    parser = argparse.ArgumentParser(
+        description="Evaluate MCP servers using test questions",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        epilog="""
+Examples:
+  # Evaluate a local stdio MCP server
+  python evaluation.py -t stdio -c python -a my_server.py eval.xml
+
+  # Evaluate an SSE MCP server
+  python evaluation.py -t sse -u https://example.com/mcp -H "Authorization: Bearer token" eval.xml
+
+  # Evaluate an HTTP MCP server with custom model
+  python evaluation.py -t http -u https://example.com/mcp -m claude-3-5-sonnet-20241022 eval.xml
+        """,
+    )
+
+    parser.add_argument("eval_file", type=Path, help="Path to evaluation XML file")
+    parser.add_argument("-t", "--transport", choices=["stdio", "sse", "http"], default="stdio", help="Transport type (default: stdio)")
+    parser.add_argument("-m", "--model", default="claude-3-7-sonnet-20250219", help="Claude model to use (default: claude-3-7-sonnet-20250219)")
+
+    stdio_group = parser.add_argument_group("stdio options")
+    stdio_group.add_argument("-c", "--command", help="Command to run MCP server (stdio only)")
+    stdio_group.add_argument("-a", "--args", nargs="+", help="Arguments for the command (stdio only)")
+    stdio_group.add_argument("-e", "--env", nargs="+", help="Environment variables in KEY=VALUE format (stdio only)")
+
+    remote_group = parser.add_argument_group("sse/http options")
+    remote_group.add_argument("-u", "--url", help="MCP server URL (sse/http only)")
+    remote_group.add_argument("-H", "--header", nargs="+", dest="headers", help="HTTP headers in 'Key: Value' format (sse/http only)")
+
+    parser.add_argument("-o", "--output", type=Path, help="Output file for evaluation report (default: stdout)")
+
+    args = parser.parse_args()
+
+    if not args.eval_file.exists():
+        print(f"Error: Evaluation file not found: {args.eval_file}")
+        sys.exit(1)
+
+    headers = parse_headers(args.headers) if args.headers else None
+    env_vars = parse_env_vars(args.env) if args.env else None
+
+    try:
+        connection = create_connection(
+            transport=args.transport,
+            command=args.command,
+            args=args.args,
+            env=env_vars,
+            url=args.url,
+            headers=headers,
+        )
+    except ValueError as e:
+        print(f"Error: {e}")
+        sys.exit(1)
+
+    print(f"🔗 Connecting to MCP server via {args.transport}...")
+
+    async with connection:
+        print("✅ Connected successfully")
+        report = await run_evaluation(args.eval_file, connection, args.model)
+
+        if args.output:
+            args.output.write_text(report)
+            print(f"\n✅ Report saved to {args.output}")
+        else:
+            print("\n" + report)
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

.claude/skills/mcp-builder/scripts/example_evaluation.xml

@@ -0,0 +1,22 @@
+<evaluation>
+   <qa_pair>
+      <question>Calculate the compound interest on $10,000 invested at 5% annual interest rate, compounded monthly for 3 years. What is the final amount in dollars (rounded to 2 decimal places)?</question>
+      <answer>11614.72</answer>
+   </qa_pair>
+   <qa_pair>
+      <question>A projectile is launched at a 45-degree angle with an initial velocity of 50 m/s. Calculate the total distance (in meters) it has traveled from the launch point after 2 seconds, assuming g=9.8 m/s². Round to 2 decimal places.</question>
+      <answer>87.25</answer>
+   </qa_pair>
+   <qa_pair>
+      <question>A sphere has a volume of 500 cubic meters. Calculate its surface area in square meters. Round to 2 decimal places.</question>
+      <answer>304.65</answer>
+   </qa_pair>
+   <qa_pair>
+      <question>Calculate the population standard deviation of this dataset: [12, 15, 18, 22, 25, 30, 35]. Round to 2 decimal places.</question>
+      <answer>7.61</answer>
+   </qa_pair>
+   <qa_pair>
+      <question>Calculate the pH of a solution with a hydrogen ion concentration of 3.5 × 10^-5 M. Round to 2 decimal places.</question>
+      <answer>4.46</answer>
+   </qa_pair>
+</evaluation>

.claude/skills/mcp-builder/scripts/requirements.txt

@@ -0,0 +1,2 @@
+anthropic>=0.39.0
+mcp>=1.1.0

.gitignore

@@ -28,9 +28,11 @@ node_modules
 
 lib
 test-dist
-docs
 
+# Claude Code
+.claude/
+CLAUDE.md
 # WebStorm
 .idea/
-
+plan/
 dist/

CHANGELOG.md

@@ -0,0 +1,250 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+---
+
+## [0.8.4] - 2026-01-04
+
+### Fixed
+- **Critical**: Added missing process error handler in `_spawnPromise()` to prevent server hang when yt-dlp is not installed or fails to spawn ([#23](https://github.com/kevinwatt/yt-dlp-mcp/issues/23))
+- **Critical**: Fixed stdout/stderr mixing in `_spawnPromise()` that caused yt-dlp warnings to corrupt parsed output
+- Fixed VERSION constant mismatch (was `0.7.0`, now synced with package.json)
+- Added try-catch for RegExp construction from `YTDLP_SANITIZE_ILLEGAL_CHARS` env var to prevent startup crash on invalid regex
+- Added validation for `YTDLP_MAX_FILENAME_LENGTH` env var to handle NaN values gracefully
+- Fixed test expectations for search output format and metadata `creators` field null handling
+
+### Changed
+- **Documentation**: Added warning about JavaScript runtime (deno) requirement when using cookie authentication
+  - YouTube authenticated API endpoints require JS challenge solving
+  - Without deno, downloads will fail with "n challenge solving failed" error
+- **Documentation**: Added version sync guidance to CLAUDE.md (package.json + src/index.mts)
+
+---
+
+## [0.8.3] - 2025-12-25
+
+### Added
+- **Video Comments Extraction**: New tools for extracting YouTube video comments
+  - `ytdlp_get_video_comments`: Extract comments in structured JSON format with author info, likes, timestamps, and reply threading
+  - `ytdlp_get_video_comments_summary`: Get human-readable summary of top comments
+  - Supports sorting by "top" (most liked) or "new" (newest first)
+  - Configurable comment limit (1-100 comments)
+  - Includes author verification status, pinned comments, and uploader replies
+  - Comprehensive test suite for comments functionality
+- **Upload Date Filter**: New `uploadDateFilter` parameter for `ytdlp_search_videos` tool ([#21](https://github.com/kevinwatt/yt-dlp-mcp/issues/21))
+  - Filter search results by upload date: `hour`, `today`, `week`, `month`, `year`
+  - Uses YouTube's native date filtering for efficient searches
+  - Optional parameter - defaults to no filtering (all dates)
+
+### Changed
+- Add Claude Code settings (.claude/, CLAUDE.md) to .gitignore
+- Add development guideline to always update CHANGELOG.md
+- Move integration test scripts to `tests/` directory for cleaner root
+- Comments integration tests are now opt-in via `RUN_INTEGRATION_TESTS=1` env var for CI stability
+
+### Fixed
+- Fixed `validateUrl()` return value not being checked in `audio.ts`, `metadata.ts`, and `video.ts`
+- Fixed comments test Python environment handling (use `delete` instead of empty string assignment)
+- Fixed regex null coalescing in comments test for author matching
+
+---
+
+## [0.7.0] - 2025-10-19
+
+### 🎉 Major Release - MCP Best Practices & Quality Improvements
+
+This release represents a significant upgrade with comprehensive MCP best practices implementation, following the official MCP server development guidelines.
+
+### ✨ Added
+
+#### Tool Naming & Organization
+- **Tool Name Prefixes**: All tools now have `ytdlp_` prefix to avoid naming conflicts with other MCP servers
+  - `search_videos` → `ytdlp_search_videos`
+  - `download_video` → `ytdlp_download_video`
+  - `get_video_metadata` → `ytdlp_get_video_metadata`
+  - And all other tools similarly prefixed
+
+#### Input Validation
+- **Zod Schema Validation**: Implemented runtime input validation for all 8 tools
+  - URL validation with proper format checking
+  - String length constraints (min/max)
+  - Number range validation
+  - Regex patterns for language codes and time formats
+  - Enum validation for resolution and format options
+  - `.strict()` mode to prevent unexpected fields
+
+#### Tool Annotations
+- **MCP Tool Hints**: Added comprehensive annotations to all tools
+  - `readOnlyHint: true` for read-only operations (search, list, get)
+  - `readOnlyHint: false` for file-creating operations (downloads)
+  - `destructiveHint: false` for all tools (no destructive updates)
+  - `idempotentHint: true/false` based on operation type
+  - `openWorldHint: true` for all tools (external API interactions)
+
+#### Response Formats
+- **Flexible Output Formats**: Added `response_format` parameter to search tools
+  - JSON format: Structured data for programmatic processing
+  - Markdown format: Human-readable display (default)
+  - Both formats include pagination metadata
+
+#### Pagination Support
+- **Search Pagination**: Added offset parameter to `ytdlp_search_videos`
+  - `offset` parameter for skipping results
+  - `has_more` indicator in responses
+  - `next_offset` for easy pagination
+  - Works with both JSON and Markdown formats
+
+#### Character Limits & Truncation
+- **Response Size Protection**: Implemented character limits to prevent context overflow
+  - Standard limit: 25,000 characters
+  - Transcript limit: 50,000 characters (larger for text content)
+  - Automatic truncation with clear messages
+  - Smart truncation that preserves JSON validity
+
+#### Error Messages
+- **Actionable Error Guidance**: Improved error messages across all modules
+  - Platform-specific errors (Unsupported URL, Video unavailable, etc.)
+  - Network error guidance with retry suggestions
+  - Language availability hints (e.g., "Use ytdlp_list_subtitle_languages to check options")
+  - Rate limit handling with wait time suggestions
+
+### 🔧 Improved
+
+#### Tool Descriptions
+- **Comprehensive Documentation**: Enhanced all tool descriptions with:
+  - Clear purpose statements
+  - Detailed parameter descriptions with examples
+  - Complete return value schemas
+  - "Use when" / "Don't use when" guidance
+  - Error handling documentation
+  - Example use cases
+
+#### Configuration
+- **Enhanced Config System**: Added new configuration options
+  - `limits.characterLimit`: Maximum response size (25,000)
+  - `limits.maxTranscriptLength`: Maximum transcript size (50,000)
+  - Environment variable support for all settings
+
+#### Code Quality
+- **Better Type Safety**: Improved TypeScript types throughout
+  - Proper type definitions for metadata with truncation fields
+  - Explicit Promise return types
+  - Better error type handling
+
+### 🐛 Fixed
+
+- **JSON Parsing Issue**: Fixed metadata truncation that was breaking JSON format
+  - Truncation messages now inside JSON objects instead of appended
+  - Prevents "Unexpected non-whitespace character" errors
+  - Maintains valid JSON structure even when truncated
+
+### 🧪 Testing
+
+- **Real-World Validation**: Comprehensive testing with actual videos
+  - ✅ YouTube platform fully tested (Rick Astley - Never Gonna Give You Up)
+  - ✅ Bilibili platform fully tested (Chinese content)
+  - ✅ Multi-language support verified (English, Chinese)
+  - ✅ All 8 tools tested with real API calls
+  - ✅ MCP protocol compatibility verified
+
+### 📖 Documentation
+
+- **Enhanced README**: Completely redesigned README.md with:
+  - Professional badges and visual formatting
+  - Comprehensive feature tables
+  - Detailed tool documentation
+  - Usage examples by category
+  - Configuration guide
+  - Architecture overview
+  - Multi-language support demonstration
+
+### 🌍 Platform Support
+
+- **Verified Platforms**:
+  - ✅ YouTube (fully tested)
+  - ✅ Bilibili (哔哩哔哩) (fully tested)
+  - 🎯 1000+ other platforms supported via yt-dlp
+
+### 📊 Statistics
+
+- 8 tools with complete Zod validation
+- 8 tools with proper annotations
+- 8 tools with comprehensive descriptions
+- 2 platforms tested and verified
+- 5/5 YouTube tests passing
+- 3/3 Bilibili tests passing
+- 0 critical bugs remaining
+
+### 🔄 Migration Guide
+
+If upgrading from 0.6.x:
+
+1. **Tool Names**: Update all tool names to include `ytdlp_` prefix
+   ```diff
+   - "search_videos"
+   + "ytdlp_search_videos"
+   ```
+
+2. **Search Parameters**: New optional parameters available
+   ```javascript
+   {
+     query: "tutorial",
+     maxResults: 10,
+     offset: 0,              // NEW: pagination support
+     response_format: "json" // NEW: format control
+   }
+   ```
+
+3. **Error Handling**: Error messages are more descriptive now
+   - Update any error parsing logic to handle new formats
+
+### 🙏 Acknowledgments
+
+This release follows the [MCP Server Development Best Practices](https://modelcontextprotocol.io) and incorporates feedback from the MCP community.
+
+---
+
+## [0.6.28] - 2025-08-13
+
+### Added
+- Video metadata extraction with `get_video_metadata` and `get_video_metadata_summary`
+- Comprehensive test suite
+- API documentation
+
+### Changed
+- Improved metadata extraction performance
+- Updated dependencies
+
+### Fixed
+- Various bug fixes and stability improvements
+
+---
+
+## [0.6.0] - 2025-08-01
+
+### Added
+- Initial MCP server implementation
+- YouTube video search functionality
+- Video download with resolution control
+- Audio extraction
+- Subtitle download and transcript generation
+- Integration with yt-dlp
+
+### Features
+- 8 core tools for video content management
+- Support for multiple video platforms
+- Configurable downloads directory
+- Automatic filename sanitization
+- Cross-platform compatibility (Windows, macOS, Linux)
+
+---
+
+[0.7.0]: https://github.com/kevinwatt/yt-dlp-mcp/compare/v0.6.28...v0.7.0
+[0.6.28]: https://github.com/kevinwatt/yt-dlp-mcp/compare/v0.6.0...v0.6.28
+[0.6.0]: https://github.com/kevinwatt/yt-dlp-mcp/releases/tag/v0.6.0

CLAUDE.md

@@ -0,0 +1,107 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Development Guidelines
+
+- **Always update CHANGELOG.md** when making changes to the codebase
+- **Version updates require TWO files**:
+  1. `package.json` - line 3: `"version": "x.x.x"`
+  2. `src/index.mts` - line 24: `const VERSION = 'x.x.x'`
+
+## Development Commands
+
+### Build and Prepare
+```bash
+npm run prepare  # Compile TypeScript and make binary executable
+```
+
+### Testing
+```bash
+npm test  # Run Jest tests with ESM support
+```
+
+### Manual Testing
+```bash
+npx @kevinwatt/yt-dlp-mcp  # Start MCP server manually
+```
+
+## Code Architecture
+
+### MCP Server Implementation
+This is an MCP (Model Context Protocol) server that integrates with `yt-dlp` for video/audio downloading. The server:
+
+- **Entry point**: `src/index.mts` - Main MCP server implementation with tool handlers
+- **Modular design**: Each feature lives in `src/modules/` (video.ts, audio.ts, subtitle.ts, search.ts, metadata.ts)
+- **Configuration**: `src/config.ts` - Centralized config with environment variable support and validation
+- **Utility functions**: `src/modules/utils.ts` - Shared spawn and cleanup utilities
+
+### Tool Architecture
+The server exposes 8 MCP tools:
+1. `search_videos` - YouTube video search
+2. `list_subtitle_languages` - List available subtitles
+3. `download_video_subtitles` - Download subtitle files  
+4. `download_video` - Download videos with resolution/trimming options
+5. `download_audio` - Extract and download audio
+6. `download_transcript` - Generate clean text transcripts
+7. `get_video_metadata` - Extract comprehensive video metadata (JSON format)
+8. `get_video_metadata_summary` - Get human-readable metadata summary
+
+### Key Patterns
+- **Unified error handling**: `handleToolExecution()` wrapper for consistent error responses
+- **Spawn management**: All external tool calls go through `_spawnPromise()` with cleanup
+- **Configuration-driven**: All defaults and behavior configurable via environment variables
+- **ESM modules**: Uses `.mts` extension and ESM imports throughout
+- **Filename sanitization**: Cross-platform safe filename handling with length limits
+- **Metadata extraction**: Uses `yt-dlp --dump-json` for comprehensive video information without downloading content
+
+### Dependencies
+- **Required external**: `yt-dlp` must be installed and in PATH
+- **Core MCP**: `@modelcontextprotocol/sdk` for server implementation
+- **Process management**: `spawn-rx` for async process spawning
+- **File operations**: `rimraf` for cleanup
+
+### Configuration System
+`CONFIG` object loaded from `config.ts` supports:
+- Download directory customization (defaults to ~/Downloads)
+- Resolution/format preferences
+- Filename sanitization rules
+- Temporary directory management
+- Environment variable overrides (YTDLP_* prefix)
+
+### Testing Setup
+- **Jest with ESM**: Custom config for TypeScript + ESM support
+- **Test isolation**: Tests run in separate environment with mocked dependencies
+- **Coverage**: Tests for each module in `src/__tests__/`
+
+### TypeScript Configuration
+- **Strict mode**: All strict TypeScript checks enabled
+- **ES2020 target**: Modern JavaScript features
+- **Declaration generation**: Types exported to `lib/` for consumption
+- **Source maps**: Enabled for debugging
+
+### Build Output
+- **Compiled code**: `lib/` directory with .js, .d.ts, and .map files
+- **Executable**: `lib/index.mjs` with shebang for direct execution
+- **Module structure**: Preserves source module organization
+
+## Metadata Module Details
+
+### VideoMetadata Interface
+The `metadata.ts` module exports a comprehensive `VideoMetadata` interface containing fields like:
+- Basic info: `id`, `title`, `description`, `duration`, `upload_date`
+- Channel info: `channel`, `channel_id`, `channel_url`, `uploader`
+- Analytics: `view_count`, `like_count`, `comment_count`
+- Technical: `formats`, `thumbnails`, `subtitles`
+- Content: `tags`, `categories`, `series`, `episode` data
+
+### Key Functions
+- `getVideoMetadata(url, fields?, config?)` - Extract full or filtered metadata as JSON
+- `getVideoMetadataSummary(url, config?)` - Generate human-readable summary
+
+### Testing
+Comprehensive test suite in `src/__tests__/metadata.test.ts` covers:
+- Field filtering and extraction
+- Error handling for invalid URLs
+- Format validation
+- Real-world integration with YouTube videos

docs/api.md

@@ -0,0 +1,194 @@
+# API Reference
+
+## Video Operations
+
+### downloadVideo(url: string, config?: Config, resolution?: string, startTime?: string, endTime?: string): Promise<string>
+
+Downloads a video from the specified URL with optional trimming.
+
+**Parameters:**
+- `url`: The URL of the video to download
+- `config`: (Optional) Configuration object
+- `resolution`: (Optional) Preferred video resolution ('480p', '720p', '1080p', 'best')
+- `startTime`: (Optional) Start time for trimming (format: HH:MM:SS[.ms])
+- `endTime`: (Optional) End time for trimming (format: HH:MM:SS[.ms])
+
+**Returns:**
+- Promise resolving to a success message with the downloaded file path
+
+**Example:**
+```javascript
+import { downloadVideo } from '@kevinwatt/yt-dlp-mcp';
+
+// Download with default settings
+const result = await downloadVideo('https://www.youtube.com/watch?v=jNQXAC9IVRw');
+console.log(result);
+
+// Download with specific resolution
+const hdResult = await downloadVideo(
+  'https://www.youtube.com/watch?v=jNQXAC9IVRw',
+  undefined,
+  '1080p'
+);
+console.log(hdResult);
+
+// Download with trimming
+const trimmedResult = await downloadVideo(
+  'https://www.youtube.com/watch?v=jNQXAC9IVRw',
+  undefined,
+  '720p',
+  '00:01:30',
+  '00:02:45'
+);
+console.log(trimmedResult);
+
+// Download with fractional seconds
+const preciseTrim = await downloadVideo(
+  'https://www.youtube.com/watch?v=jNQXAC9IVRw',
+  undefined,
+  '720p',
+  '00:01:30.500',
+  '00:02:45.250'
+);
+console.log(preciseTrim);
+```
+
+## Audio Operations
+
+### downloadAudio(url: string, config?: Config): Promise<string>
+
+Downloads audio from the specified URL in the best available quality.
+
+**Parameters:**
+- `url`: The URL of the video to extract audio from
+- `config`: (Optional) Configuration object
+
+**Returns:**
+- Promise resolving to a success message with the downloaded file path
+
+**Example:**
+```javascript
+import { downloadAudio } from '@kevinwatt/yt-dlp-mcp';
+
+const result = await downloadAudio('https://www.youtube.com/watch?v=jNQXAC9IVRw');
+console.log(result);
+```
+
+## Subtitle Operations
+
+### listSubtitles(url: string): Promise<string>
+
+Lists all available subtitles for a video.
+
+**Parameters:**
+- `url`: The URL of the video
+
+**Returns:**
+- Promise resolving to a string containing the list of available subtitles
+
+**Example:**
+```javascript
+import { listSubtitles } from '@kevinwatt/yt-dlp-mcp';
+
+const subtitles = await listSubtitles('https://www.youtube.com/watch?v=jNQXAC9IVRw');
+console.log(subtitles);
+```
+
+### downloadSubtitles(url: string, language: string): Promise<string>
+
+Downloads subtitles for a video in the specified language.
+
+**Parameters:**
+- `url`: The URL of the video
+- `language`: Language code (e.g., 'en', 'zh-Hant', 'ja')
+
+**Returns:**
+- Promise resolving to the subtitle content
+
+**Example:**
+```javascript
+import { downloadSubtitles } from '@kevinwatt/yt-dlp-mcp';
+
+const subtitles = await downloadSubtitles(
+  'https://www.youtube.com/watch?v=jNQXAC9IVRw',
+  'en'
+);
+console.log(subtitles);
+```
+
+## Metadata Operations
+
+### getVideoMetadata(url: string, fields?: string[]): Promise<string>
+
+Extract comprehensive video metadata using yt-dlp without downloading the content.
+
+**Parameters:**
+- `url`: The URL of the video to extract metadata from
+- `fields`: (Optional) Specific metadata fields to extract (e.g., `['id', 'title', 'description', 'channel']`). If omitted, returns all available metadata. If provided as an empty array `[]`, returns `{}`.
+
+**Returns:**
+- Promise resolving to a JSON string of metadata (pretty-printed)
+
+**Example:**
+```javascript
+import { getVideoMetadata } from '@kevinwatt/yt-dlp-mcp';
+
+// Get all metadata
+const all = await getVideoMetadata('https://www.youtube.com/watch?v=jNQXAC9IVRw');
+console.log(all);
+
+// Get specific fields only
+const subset = await getVideoMetadata(
+  'https://www.youtube.com/watch?v=jNQXAC9IVRw',
+  ['id', 'title', 'description', 'channel']
+);
+console.log(subset);
+```
+
+### getVideoMetadataSummary(url: string): Promise<string>
+
+Get a human-readable summary of key video metadata fields.
+
+**Parameters:**
+- `url`: The URL of the video
+
+**Returns:**
+- Promise resolving to a formatted text summary (title, channel, duration, views, upload date, description preview, etc.)
+
+**Example:**
+```javascript
+import { getVideoMetadataSummary } from '@kevinwatt/yt-dlp-mcp';
+
+const summary = await getVideoMetadataSummary('https://www.youtube.com/watch?v=jNQXAC9IVRw');
+console.log(summary);
+```
+
+## Configuration
+
+### Config Interface
+
+```typescript
+interface Config {
+  file: {
+    maxFilenameLength: number;
+    downloadsDir: string;
+    tempDirPrefix: string;
+    sanitize: {
+      replaceChar: string;
+      truncateSuffix: string;
+      illegalChars: RegExp;
+      reservedNames: readonly string[];
+    };
+  };
+  tools: {
+    required: readonly string[];
+  };
+  download: {
+    defaultResolution: "480p" | "720p" | "1080p" | "best";
+    defaultAudioFormat: "m4a" | "mp3";
+    defaultSubtitleLanguage: string;
+  };
+}
+```
+
+For detailed configuration options, see [Configuration Guide](./configuration.md). 

docs/configuration.md

@@ -0,0 +1,169 @@
+# Configuration Guide
+
+## Overview
+
+The yt-dlp-mcp package can be configured through environment variables or by passing a configuration object to the functions.
+
+## Configuration Object
+
+```typescript
+interface Config {
+  file: {
+    maxFilenameLength: number;
+    downloadsDir: string;
+    tempDirPrefix: string;
+    sanitize: {
+      replaceChar: string;
+      truncateSuffix: string;
+      illegalChars: RegExp;
+      reservedNames: readonly string[];
+    };
+  };
+  tools: {
+    required: readonly string[];
+  };
+  download: {
+    defaultResolution: "480p" | "720p" | "1080p" | "best";
+    defaultAudioFormat: "m4a" | "mp3";
+    defaultSubtitleLanguage: string;
+  };
+}
+```
+
+## Environment Variables
+
+| Variable | Description | Default |
+|----------|-------------|---------|
+| `YTDLP_MAX_FILENAME_LENGTH` | Maximum length for filenames | 50 |
+| `YTDLP_DOWNLOADS_DIR` | Download directory path | `~/Downloads` |
+| `YTDLP_TEMP_DIR_PREFIX` | Prefix for temporary directories | `ytdlp-` |
+| `YTDLP_SANITIZE_REPLACE_CHAR` | Character to replace illegal characters | `_` |
+| `YTDLP_SANITIZE_TRUNCATE_SUFFIX` | Suffix for truncated filenames | `...` |
+| `YTDLP_SANITIZE_ILLEGAL_CHARS` | Regex pattern for illegal characters | `/[<>:"/\\|?*\x00-\x1F]/g` |
+| `YTDLP_SANITIZE_RESERVED_NAMES` | Comma-separated list of reserved names | `CON,PRN,AUX,...` |
+| `YTDLP_DEFAULT_RESOLUTION` | Default video resolution | `720p` |
+| `YTDLP_DEFAULT_AUDIO_FORMAT` | Default audio format | `m4a` |
+| `YTDLP_DEFAULT_SUBTITLE_LANG` | Default subtitle language | `en` |
+
+## File Configuration
+
+### Download Directory
+
+The download directory can be configured in two ways:
+
+1. Environment variable:
+```bash
+export YTDLP_DOWNLOADS_DIR="/path/to/downloads"
+```
+
+2. Configuration object:
+```javascript
+const config = {
+  file: {
+    downloadsDir: "/path/to/downloads"
+  }
+};
+```
+
+### Filename Sanitization
+
+Control how filenames are sanitized:
+
+```javascript
+const config = {
+  file: {
+    maxFilenameLength: 100,
+    sanitize: {
+      replaceChar: '-',
+      truncateSuffix: '___',
+      illegalChars: /[<>:"/\\|?*\x00-\x1F]/g,
+      reservedNames: ['CON', 'PRN', 'AUX', 'NUL']
+    }
+  }
+};
+```
+
+## Download Configuration
+
+### Video Resolution
+
+Set default video resolution:
+
+```javascript
+const config = {
+  download: {
+    defaultResolution: "1080p" // "480p" | "720p" | "1080p" | "best"
+  }
+};
+```
+
+### Audio Format
+
+Configure audio format preferences:
+
+```javascript
+const config = {
+  download: {
+    defaultAudioFormat: "m4a" // "m4a" | "mp3"
+  }
+};
+```
+
+### Subtitle Language
+
+Set default subtitle language:
+
+```javascript
+const config = {
+  download: {
+    defaultSubtitleLanguage: "en"
+  }
+};
+```
+
+## Tools Configuration
+
+Configure required external tools:
+
+```javascript
+const config = {
+  tools: {
+    required: ['yt-dlp']
+  }
+};
+```
+
+## Complete Configuration Example
+
+```javascript
+import { CONFIG } from '@kevinwatt/yt-dlp-mcp';
+
+const customConfig = {
+  file: {
+    maxFilenameLength: 100,
+    downloadsDir: '/custom/downloads',
+    tempDirPrefix: 'ytdlp-temp-',
+    sanitize: {
+      replaceChar: '-',
+      truncateSuffix: '___',
+      illegalChars: /[<>:"/\\|?*\x00-\x1F]/g,
+      reservedNames: [
+        'CON', 'PRN', 'AUX', 'NUL',
+        'COM1', 'COM2', 'COM3', 'COM4', 'COM5',
+        'LPT1', 'LPT2', 'LPT3'
+      ]
+    }
+  },
+  tools: {
+    required: ['yt-dlp']
+  },
+  download: {
+    defaultResolution: '1080p',
+    defaultAudioFormat: 'm4a',
+    defaultSubtitleLanguage: 'en'
+  }
+};
+
+// Use the custom configuration
+const result = await downloadVideo(url, customConfig);
+``` 

docs/contributing.md

@@ -0,0 +1,198 @@
+# Contributing Guide
+
+## Getting Started
+
+1. Fork the repository
+2. Clone your fork:
+
+```bash
+git clone https://github.com/your-username/yt-dlp-mcp.git
+cd yt-dlp-mcp
+```
+
+3. Install dependencies:
+
+```bash
+npm install
+```
+
+4. Create a new branch:
+
+```bash
+git checkout -b feature/your-feature-name
+```
+
+## Development Setup
+
+### Prerequisites
+
+- Node.js 16.x or higher
+- yt-dlp installed on your system
+- TypeScript knowledge
+- Jest for testing
+
+### Building
+
+```bash
+npm run prepare
+```
+
+### Running Tests
+
+```bash
+npm test
+```
+
+For specific test files:
+
+```bash
+npm test -- src/__tests__/video.test.ts
+```
+
+## Code Style
+
+We use TypeScript and follow these conventions:
+
+- Use meaningful variable and function names
+- Add JSDoc comments for public APIs
+- Follow the existing code style
+- Use async/await for promises
+- Handle errors appropriately
+
+### TypeScript Guidelines
+
+```typescript
+// Use explicit types
+function downloadVideo(url: string, config?: Config): Promise<string> {
+  // Implementation
+}
+
+// Use interfaces for complex types
+interface DownloadOptions {
+  resolution: string;
+  format: string;
+  output: string;
+}
+
+// Use enums for fixed values
+enum Resolution {
+  SD = "480p",
+  HD = "720p",
+  FHD = "1080p",
+  BEST = "best",
+}
+```
+
+## Testing
+
+### Writing Tests
+
+- Place tests in `src/__tests__` directory
+- Name test files with `.test.ts` suffix
+- Use descriptive test names
+- Test both success and error cases
+
+Example:
+
+```typescript
+describe("downloadVideo", () => {
+  test("downloads video successfully", async () => {
+    const result = await downloadVideo(testUrl);
+    expect(result).toMatch(/Video successfully downloaded/);
+  });
+
+  test("handles invalid URL", async () => {
+    await expect(downloadVideo("invalid-url")).rejects.toThrow(
+      "Invalid or unsupported URL"
+    );
+  });
+});
+```
+
+### Test Coverage
+
+Aim for high test coverage:
+
+```bash
+npm run test:coverage
+```
+
+## Documentation
+
+### JSDoc Comments
+
+Add comprehensive JSDoc comments for all public APIs:
+
+````typescript
+/**
+ * Downloads a video from the specified URL.
+ *
+ * @param url - The URL of the video to download
+ * @param config - Optional configuration object
+ * @param resolution - Preferred video resolution
+ * @returns Promise resolving to success message with file path
+ * @throws {Error} When URL is invalid or download fails
+ *
+ * @example
+ * ```typescript
+ * const result = await downloadVideo('https://youtube.com/watch?v=...', config);
+ * console.log(result);
+ * ```
+ */
+export async function downloadVideo(
+  url: string,
+  config?: Config,
+  resolution?: string
+): Promise<string> {
+  // Implementation
+}
+````
+
+### README Updates
+
+- Update README.md for new features
+- Keep examples up to date
+- Document breaking changes
+
+## Pull Request Process
+
+1. Update tests and documentation
+2. Run all tests and linting
+3. Update CHANGELOG.md
+4. Create detailed PR description
+5. Reference related issues
+
+### PR Checklist
+
+- [ ] Tests added/updated
+- [ ] Documentation updated
+- [ ] CHANGELOG.md updated
+- [ ] Code follows style guidelines
+- [ ] All tests passing
+- [ ] No linting errors
+
+## Release Process
+
+1. Update version in package.json
+2. Update CHANGELOG.md
+3. Create release commit
+4. Tag release
+5. Push to main branch
+
+### Version Numbers
+
+Follow semantic versioning:
+
+- MAJOR: Breaking changes
+- MINOR: New features
+- PATCH: Bug fixes
+
+## Community
+
+- Be respectful and inclusive
+- Help others when possible
+- Report bugs with detailed information
+- Suggest improvements
+- Share success stories
+
+For more information, see the [README](./README.md) and [API Reference](./api.md).

docs/cookies.md

@@ -0,0 +1,302 @@
+# Cookies Configuration Guide
+
+## Why Do You Need Cookies?
+
+You need to configure cookies for yt-dlp-mcp in the following situations:
+
+- **Access private videos**: Videos that require login to view
+- **Age-restricted content**: Content requiring account age verification
+- **Bypass CAPTCHA**: Some websites require verification
+- **Avoid rate limiting**: Reduce HTTP 429 (Too Many Requests) errors
+- **YouTube Premium features**: Access premium-exclusive content and quality
+
+## Configuration Methods
+
+yt-dlp-mcp supports two cookie configuration methods via environment variables.
+
+### Method 1: Extract from Browser (Recommended)
+
+This is the simplest approach. yt-dlp reads cookies directly from your browser.
+
+```bash
+YTDLP_COOKIES_FROM_BROWSER=chrome
+```
+
+#### Supported Browsers
+
+| Browser | Value |
+|---------|-------|
+| Google Chrome | `chrome` |
+| Chromium | `chromium` |
+| Microsoft Edge | `edge` |
+| Mozilla Firefox | `firefox` |
+| Brave | `brave` |
+| Opera | `opera` |
+| Safari (macOS) | `safari` |
+| Vivaldi | `vivaldi` |
+| Whale | `whale` |
+
+#### Advanced Configuration
+
+```bash
+# Specify Chrome Profile
+YTDLP_COOKIES_FROM_BROWSER=chrome:Profile 1
+
+# Specify Firefox Container
+YTDLP_COOKIES_FROM_BROWSER=firefox::work
+
+# Flatpak-installed Chrome (Linux)
+YTDLP_COOKIES_FROM_BROWSER=chrome:~/.var/app/com.google.Chrome/
+
+# Full format: BROWSER:PROFILE::CONTAINER
+YTDLP_COOKIES_FROM_BROWSER=chrome:Profile 1::personal
+```
+
+### Method 2: Use Cookie File
+
+If you prefer using a fixed cookie file, or automatic extraction doesn't work:
+
+```bash
+YTDLP_COOKIES_FILE=/path/to/cookies.txt
+```
+
+The cookie file must be in Netscape/Mozilla format with the first line:
+```
+# Netscape HTTP Cookie File
+```
+
+## Exporting Cookies
+
+### Using yt-dlp (Recommended)
+
+This is the most reliable method, ensuring correct format:
+
+```bash
+# Export from Chrome
+yt-dlp --cookies-from-browser chrome --cookies cookies.txt "https://www.youtube.com"
+
+# Export from Firefox
+yt-dlp --cookies-from-browser firefox --cookies cookies.txt "https://www.youtube.com"
+```
+
+> **Note**: This command exports ALL website cookies from your browser. Keep this file secure.
+
+### Using Browser Extensions
+
+| Browser | Extension |
+|---------|-----------|
+| Chrome | [Get cookies.txt LOCALLY](https://chrome.google.com/webstore/detail/get-cookiestxt-locally/cclelndahbckbenkjhflpdbgdldlbecc) |
+| Firefox | [cookies.txt](https://addons.mozilla.org/firefox/addon/cookies-txt/) |
+
+> **Warning**: Only use the recommended extensions above. Some cookie export extensions may be malware.
+
+## MCP Configuration Examples
+
+### Claude Desktop
+
+Edit `claude_desktop_config.json`:
+
+**Using Browser Cookies:**
+```json
+{
+  "mcpServers": {
+    "yt-dlp": {
+      "command": "npx",
+      "args": ["@kevinwatt/yt-dlp-mcp"],
+      "env": {
+        "YTDLP_COOKIES_FROM_BROWSER": "chrome"
+      }
+    }
+  }
+}
+```
+
+**Using Cookie File:**
+```json
+{
+  "mcpServers": {
+    "yt-dlp": {
+      "command": "npx",
+      "args": ["@kevinwatt/yt-dlp-mcp"],
+      "env": {
+        "YTDLP_COOKIES_FILE": "/Users/username/.config/yt-dlp/cookies.txt"
+      }
+    }
+  }
+}
+```
+
+### Configuration File Locations
+
+| OS | Claude Desktop Config Location |
+|----|-------------------------------|
+| macOS | `~/Library/Application Support/Claude/claude_desktop_config.json` |
+| Windows | `%APPDATA%\Claude\claude_desktop_config.json` |
+| Linux | `~/.config/Claude/claude_desktop_config.json` |
+
+## Priority Order
+
+When both `YTDLP_COOKIES_FILE` and `YTDLP_COOKIES_FROM_BROWSER` are set:
+
+1. `YTDLP_COOKIES_FILE` is used first
+2. If no file is set, `YTDLP_COOKIES_FROM_BROWSER` is used
+
+## Security Best Practices
+
+### Cookie File Security
+
+1. **Keep it safe**: Cookie files contain your login credentials; leakage may lead to account compromise
+2. **Never share**: Never share cookie files with others or upload to public locations
+3. **Version control**: Add `cookies.txt` to `.gitignore`
+4. **File permissions**:
+   ```bash
+   chmod 600 cookies.txt  # Owner read/write only
+   ```
+
+### Browser Cookie Extraction
+
+- Ensure your browser is up to date
+- You may need to close the browser temporarily during extraction
+- Some browser security features may block cookie extraction
+
+### Regular Updates
+
+- Browser cookies expire
+- Re-export cookies periodically
+- If you encounter authentication errors, try updating cookies
+
+## Troubleshooting
+
+### Error: Cookie file not found
+
+```
+Error: Cookie file not found: /path/to/cookies.txt
+```
+
+**Solutions:**
+1. Verify the file path is correct
+2. Confirm the file exists
+3. Ensure the MCP service has permission to read the file
+
+### Error: Browser cookies could not be loaded
+
+```
+Error: Could not load cookies from chrome
+```
+
+**Solutions:**
+1. Verify browser name spelling is correct
+2. Try closing the browser and retry
+3. Ensure no multiple browser instances are running
+4. Check if browser has password-protected cookie storage
+
+### Error: Invalid cookie file format
+
+```
+Error: Invalid cookie file format
+```
+
+**Solutions:**
+1. Ensure first line is `# Netscape HTTP Cookie File` or `# HTTP Cookie File`
+2. Check line ending format (Unix uses LF, Windows uses CRLF)
+3. Re-export cookies using yt-dlp
+
+### Still Cannot Access Private Videos
+
+1. **Confirm login**: Verify you're logged in to the video platform in your browser
+2. **Refresh page**: Refresh the video page in browser before exporting
+3. **Re-export**: Re-export cookies
+4. **Check permissions**: Confirm your account has permission to access the video
+
+### HTTP 400: Bad Request
+
+This usually indicates incorrect line ending format in the cookie file.
+
+**Linux/macOS:**
+```bash
+# Convert to Unix line endings
+sed -i 's/\r$//' cookies.txt
+```
+
+**Windows:**
+Use Notepad++ or VS Code to convert line endings to LF.
+
+## YouTube JavaScript Runtime Requirement
+
+YouTube requires a JavaScript runtime for yt-dlp to function properly. Without it, you may see errors like:
+
+```
+WARNING: [youtube] Signature solving failed: Some formats may be missing
+ERROR: Requested format is not available
+```
+
+### Installing EJS (Recommended)
+
+EJS is a lightweight JavaScript runtime specifically designed for yt-dlp.
+
+**Linux (Debian/Ubuntu):**
+```bash
+# Install Node.js if not already installed
+sudo apt install nodejs
+
+# Install EJS globally
+sudo npm install -g @aspect-build/ejs
+```
+
+**Linux (Arch):**
+```bash
+sudo pacman -S nodejs npm
+sudo npm install -g @aspect-build/ejs
+```
+
+**macOS:**
+```bash
+brew install node
+npm install -g @aspect-build/ejs
+```
+
+**Windows:**
+```powershell
+# Install Node.js from https://nodejs.org/
+npm install -g @aspect-build/ejs
+```
+
+### Alternative: PhantomJS
+
+If EJS doesn't work, you can try PhantomJS:
+
+**Linux:**
+```bash
+sudo apt install phantomjs
+```
+
+**macOS:**
+```bash
+brew install phantomjs
+```
+
+### Verifying Installation
+
+Test that yt-dlp can use the JavaScript runtime:
+
+```bash
+yt-dlp --dump-json "https://www.youtube.com/watch?v=dQw4w9WgXcQ" 2>&1 | head -1
+```
+
+If successful, you should see JSON output starting with `{`.
+
+### Additional Dependencies for Cookie Extraction (Linux)
+
+On Linux, cookie extraction from browsers requires the `secretstorage` module:
+
+```bash
+python3 -m pip install secretstorage
+```
+
+This is needed to decrypt cookies stored by Chromium-based browsers.
+
+## Related Links
+
+- [yt-dlp Cookie FAQ](https://github.com/yt-dlp/yt-dlp/wiki/FAQ#how-do-i-pass-cookies-to-yt-dlp)
+- [yt-dlp EJS Wiki](https://github.com/yt-dlp/yt-dlp/wiki/EJS)
+- [yt-dlp Documentation](https://github.com/yt-dlp/yt-dlp#readme)

docs/error-handling.md

@@ -0,0 +1,175 @@
+# Error Handling Guide
+
+## Common Errors
+
+### Invalid URL
+
+When providing an invalid or unsupported URL:
+
+```javascript
+try {
+  await downloadVideo('invalid-url');
+} catch (error) {
+  if (error.message.includes('Invalid or unsupported URL')) {
+    console.error('Please provide a valid YouTube or supported platform URL');
+  }
+}
+```
+
+### Missing Subtitles
+
+When trying to download unavailable subtitles:
+
+```javascript
+try {
+  await downloadSubtitles(url, 'en');
+} catch (error) {
+  if (error.message.includes('No subtitle files found')) {
+    console.warn('No subtitles available in the requested language');
+  }
+}
+```
+
+### yt-dlp Command Failures
+
+When yt-dlp command execution fails:
+
+```javascript
+try {
+  await downloadVideo(url);
+} catch (error) {
+  if (error.message.includes('Failed with exit code')) {
+    console.error('yt-dlp command failed:', error.message);
+    // Check if yt-dlp is installed and up to date
+  }
+}
+```
+
+### File System Errors
+
+When encountering file system issues:
+
+```javascript
+try {
+  await downloadVideo(url);
+} catch (error) {
+  if (error.message.includes('No write permission')) {
+    console.error('Cannot write to downloads directory. Check permissions.');
+  } else if (error.message.includes('Cannot create temporary directory')) {
+    console.error('Cannot create temporary directory. Check system temp directory permissions.');
+  }
+}
+```
+
+## Comprehensive Error Handler
+
+Here's a comprehensive error handler that covers most common scenarios:
+
+```javascript
+async function handleDownload(url, options = {}) {
+  try {
+    // Attempt the download
+    const result = await downloadVideo(url, options);
+    return result;
+  } catch (error) {
+    // URL validation errors
+    if (error.message.includes('Invalid or unsupported URL')) {
+      throw new Error(`Invalid URL: ${url}. Please provide a valid video URL.`);
+    }
+
+    // File system errors
+    if (error.message.includes('No write permission')) {
+      throw new Error(`Permission denied: Cannot write to ${options.file?.downloadsDir || '~/Downloads'}`);
+    }
+    if (error.message.includes('Cannot create temporary directory')) {
+      throw new Error('Cannot create temporary directory. Check system permissions.');
+    }
+
+    // yt-dlp related errors
+    if (error.message.includes('Failed with exit code')) {
+      if (error.message.includes('This video is unavailable')) {
+        throw new Error('Video is unavailable or has been removed.');
+      }
+      if (error.message.includes('Video is private')) {
+        throw new Error('This video is private and cannot be accessed.');
+      }
+      throw new Error('Download failed. Please check if yt-dlp is installed and up to date.');
+    }
+
+    // Subtitle related errors
+    if (error.message.includes('No subtitle files found')) {
+      throw new Error(`No subtitles available in ${options.language || 'the requested language'}.`);
+    }
+
+    // Unknown errors
+    throw new Error(`Unexpected error: ${error.message}`);
+  }
+}
+```
+
+## Error Prevention
+
+### URL Validation
+
+Always validate URLs before processing:
+
+```javascript
+import { validateUrl, isYouTubeUrl } from '@kevinwatt/yt-dlp-mcp';
+
+function validateVideoUrl(url) {
+  if (!validateUrl(url)) {
+    throw new Error('Invalid URL format');
+  }
+  
+  if (!isYouTubeUrl(url)) {
+    console.warn('URL is not from YouTube, some features might not work');
+  }
+}
+```
+
+### Configuration Validation
+
+Validate configuration before use:
+
+```javascript
+function validateConfig(config) {
+  if (!config.file.downloadsDir) {
+    throw new Error('Downloads directory must be specified');
+  }
+
+  if (config.file.maxFilenameLength < 5) {
+    throw new Error('Filename length must be at least 5 characters');
+  }
+
+  if (!['480p', '720p', '1080p', 'best'].includes(config.download.defaultResolution)) {
+    throw new Error('Invalid resolution specified');
+  }
+}
+```
+
+### Safe Cleanup
+
+Always use safe cleanup for temporary files:
+
+```javascript
+import { safeCleanup } from '@kevinwatt/yt-dlp-mcp';
+
+try {
+  // Your download code here
+} catch (error) {
+  console.error('Download failed:', error);
+} finally {
+  await safeCleanup(tempDir);
+}
+```
+
+## Best Practices
+
+1. Always wrap async operations in try-catch blocks
+2. Validate inputs before processing
+3. Use specific error types for different scenarios
+4. Clean up temporary files in finally blocks
+5. Log errors appropriately for debugging
+6. Provide meaningful error messages to users
+
+For more information about specific errors and their solutions, see the [API Reference](./api.md). 

docs/search-feature-demo.md

@@ -0,0 +1,77 @@
+# Search Feature Demo
+
+The search functionality has been successfully added to yt-dlp-mcp! This feature allows you to search for videos on YouTube using keywords and get formatted results with video information.
+
+## New Tool: `search_videos`
+
+### Description
+Search for videos on YouTube using keywords. Returns title, uploader, duration, and URL for each result.
+
+### Parameters
+- `query` (string, required): Search keywords or phrase
+- `maxResults` (number, optional): Maximum number of results to return (1-50, default: 10)
+
+### Example Usage
+
+Ask your LLM to:
+```
+"Search for Python tutorial videos"
+"Find JavaScript courses and show me the top 5 results"
+"Search for machine learning tutorials with 15 results"
+```
+
+### Example Output
+
+When searching for "javascript tutorial" with 3 results, you'll get:
+
+```
+Found 3 videos:
+
+1. **JavaScript Tutorial Full Course - Beginner to Pro**
+   📺 Channel: Traversy Media
+   ⏱️  Duration: 15663
+   🔗 URL: https://www.youtube.com/watch?v=EerdGm-ehJQ
+   🆔 ID: EerdGm-ehJQ
+
+2. **JavaScript Course for Beginners**
+   📺 Channel: FreeCodeCamp.org
+   ⏱️  Duration: 12402
+   🔗 URL: https://www.youtube.com/watch?v=W6NZfCO5SIk
+   🆔 ID: W6NZfCO5SIk
+
+3. **JavaScript Full Course for free 🌐 (2024)**
+   📺 Channel: Bro Code
+   ⏱️  Duration: 43200
+   🔗 URL: https://www.youtube.com/watch?v=lfmg-EJ8gm4
+   🆔 ID: lfmg-EJ8gm4
+
+💡 You can use any URL to download videos, audio, or subtitles!
+```
+
+## Integration with Existing Features
+
+After searching for videos, you can directly use the returned URLs with other tools:
+
+1. **Download video**: Use the URL with `download_video`
+2. **Download audio**: Use the URL with `download_audio`
+3. **Get subtitles**: Use the URL with `list_subtitle_languages` or `download_video_subtitles`
+4. **Get transcript**: Use the URL with `download_transcript`
+
+## Test Results
+
+All search functionality tests pass:
+- ✅ Successfully search and format results
+- ✅ Reject empty search queries
+- ✅ Validate maxResults parameter range
+- ✅ Handle search with different result counts
+- ✅ Return properly formatted results
+- ✅ Handle obscure search terms gracefully
+
+## Implementation Details
+
+The search feature uses yt-dlp's built-in search capability with the syntax:
+- `ytsearch[N]:[query]` where N is the number of results
+- Uses `--print` options to extract: title, id, uploader, duration
+- Results are formatted in a user-friendly way with emojis and clear structure
+
+This addresses the feature request from [Issue #14](https://github.com/kevinwatt/yt-dlp-mcp/issues/14) and provides a seamless search experience for users. 

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@kevinwatt/yt-dlp-mcp",
-  "version": "0.6.20",
-  "description": "yt-dlp MCP Server - Download video content via Model Context Protocol",
+  "version": "0.8.4",
+  "description": "An MCP server implementation that integrates with yt-dlp, providing video and audio content download capabilities (e.g. YouTube, Facebook, Tiktok, etc.) for LLMs.",
   "keywords": [
     "mcp",
     "youtube",
@@ -26,8 +26,8 @@
   ],
   "main": "./lib/index.mjs",
   "scripts": {
-    "prepare": "tsc && shx chmod +x ./lib/index.mjs",
-    "test": "node --experimental-vm-modules node_modules/jest/bin/jest.js --detectOpenHandles --forceExit"
+    "prepare": "tsc --skipLibCheck && chmod +x ./lib/index.mjs",
+    "test": "PYTHONPATH= PYTHONHOME= node --experimental-vm-modules node_modules/jest/bin/jest.js --detectOpenHandles --forceExit"
   },
   "author": "Dewei Yen <k@funmula.com>",
   "license": "MIT",
@@ -40,7 +40,8 @@
   "dependencies": {
     "@modelcontextprotocol/sdk": "0.7.0",
     "rimraf": "^6.0.1",
-    "spawn-rx": "^4.0.0"
+    "spawn-rx": "^4.0.0",
+    "zod": "^4.1.12"
   },
   "devDependencies": {
     "@jest/globals": "^29.7.0",

src/__tests__/audio.test.ts

@@ -0,0 +1,43 @@
+// @ts-nocheck
+// @jest-environment node
+import { describe, test, expect } from '@jest/globals';
+import * as os from 'os';
+import * as path from 'path';
+import { downloadAudio } from '../modules/audio.js';
+import { CONFIG } from '../config.js';
+import * as fs from 'fs';
+
+describe('downloadAudio', () => {
+  const testUrl = 'https://www.youtube.com/watch?v=jNQXAC9IVRw';
+  const testConfig = {
+    ...CONFIG,
+    file: {
+      ...CONFIG.file,
+      downloadsDir: path.join(os.tmpdir(), 'yt-dlp-test-downloads'),
+      tempDirPrefix: 'yt-dlp-test-'
+    }
+  };
+
+  beforeAll(async () => {
+    await fs.promises.mkdir(testConfig.file.downloadsDir, { recursive: true });
+  });
+
+  afterAll(async () => {
+    await fs.promises.rm(testConfig.file.downloadsDir, { recursive: true, force: true });
+  });
+
+  test('downloads audio successfully from YouTube', async () => {
+    const result = await downloadAudio(testUrl, testConfig);
+    expect(result).toContain('Audio successfully downloaded');
+    
+    const files = await fs.promises.readdir(testConfig.file.downloadsDir);
+    expect(files.length).toBeGreaterThan(0);
+    expect(files[0]).toMatch(/\.m4a$/);
+  }, 30000);
+
+  test('handles invalid URL', async () => {
+    await expect(downloadAudio('invalid-url', testConfig))
+      .rejects
+      .toThrow();
+  });
+}); 

src/__tests__/comments.test.ts

@@ -0,0 +1,180 @@
+// @ts-nocheck
+// @jest-environment node
+import { describe, test, expect, beforeAll } from '@jest/globals';
+import { getVideoComments, getVideoCommentsSummary } from '../modules/comments.js';
+import type { CommentsResponse } from '../modules/comments.js';
+import { CONFIG } from '../config.js';
+
+// Clear Python environment to avoid yt-dlp issues
+delete process.env.PYTHONPATH;
+delete process.env.PYTHONHOME;
+
+// Integration tests require network access - opt-in via RUN_INTEGRATION_TESTS=1
+const RUN_INTEGRATION = process.env.RUN_INTEGRATION_TESTS === '1';
+
+(RUN_INTEGRATION ? describe : describe.skip)('Video Comments Extraction', () => {
+  // Using a popular video that should have comments enabled
+  const testUrl = 'https://www.youtube.com/watch?v=jNQXAC9IVRw';
+
+  describe('getVideoComments', () => {
+    test('should extract comments from YouTube video', async () => {
+      const commentsJson = await getVideoComments(testUrl, 5, 'top', CONFIG);
+      const data: CommentsResponse = JSON.parse(commentsJson);
+
+      // Verify response structure
+      expect(data).toHaveProperty('count');
+      expect(data).toHaveProperty('has_more');
+      expect(data).toHaveProperty('comments');
+      expect(Array.isArray(data.comments)).toBe(true);
+      expect(data.count).toBeGreaterThan(0);
+      expect(data.count).toBeLessThanOrEqual(5);
+    }, 60000);
+
+    test('should return comments with expected fields', async () => {
+      const commentsJson = await getVideoComments(testUrl, 3, 'top', CONFIG);
+      const data: CommentsResponse = JSON.parse(commentsJson);
+
+      if (data.comments.length > 0) {
+        const comment = data.comments[0];
+
+        // These fields should typically be present
+        expect(comment).toHaveProperty('text');
+        expect(comment).toHaveProperty('author');
+
+        // Verify text is a string
+        if (comment.text !== undefined) {
+          expect(typeof comment.text).toBe('string');
+        }
+        if (comment.author !== undefined) {
+          expect(typeof comment.author).toBe('string');
+        }
+      }
+    }, 60000);
+
+    test('should respect maxComments parameter', async () => {
+      const commentsJson = await getVideoComments(testUrl, 3, 'top', CONFIG);
+      const data: CommentsResponse = JSON.parse(commentsJson);
+
+      expect(data.comments.length).toBeLessThanOrEqual(3);
+    }, 60000);
+
+    test('should support different sort orders', async () => {
+      // Just verify both sort orders work without error
+      const topComments = await getVideoComments(testUrl, 2, 'top', CONFIG);
+      const topData: CommentsResponse = JSON.parse(topComments);
+      expect(topData).toHaveProperty('comments');
+
+      const newComments = await getVideoComments(testUrl, 2, 'new', CONFIG);
+      const newData: CommentsResponse = JSON.parse(newComments);
+      expect(newData).toHaveProperty('comments');
+    }, 90000);
+
+    test('should throw error for invalid URL', async () => {
+      await expect(getVideoComments('invalid-url', 5, 'top', CONFIG)).rejects.toThrow();
+    });
+
+    test('should throw error for unsupported URL', async () => {
+      await expect(getVideoComments('https://example.com/video', 5, 'top', CONFIG)).rejects.toThrow();
+    }, 30000);
+  });
+
+  describe('getVideoCommentsSummary', () => {
+    test('should generate human-readable summary', async () => {
+      const summary = await getVideoCommentsSummary(testUrl, 5, CONFIG);
+
+      expect(typeof summary).toBe('string');
+      expect(summary.length).toBeGreaterThan(0);
+
+      // Should contain header
+      expect(summary).toContain('Video Comments');
+
+      // Should have formatted content
+      expect(summary).toContain('Author:');
+    }, 60000);
+
+    test('should respect maxComments parameter', async () => {
+      const summary = await getVideoCommentsSummary(testUrl, 3, CONFIG);
+
+      // Count occurrences of "Author:" to verify number of comments
+      const authorMatches = summary.match(/Author:/g) ?? [];
+      expect(authorMatches.length).toBeLessThanOrEqual(3);
+    }, 60000);
+
+    test('should throw error for invalid URL', async () => {
+      await expect(getVideoCommentsSummary('invalid-url', 5, CONFIG)).rejects.toThrow();
+    });
+
+    test('should handle videos with different comment counts', async () => {
+      const summary = await getVideoCommentsSummary(testUrl, 10, CONFIG);
+
+      // Summary should be a valid string
+      expect(typeof summary).toBe('string');
+      expect(summary.trim().length).toBeGreaterThan(0);
+    }, 60000);
+  });
+
+  describe('Error Handling', () => {
+    test('should provide helpful error message for unavailable video', async () => {
+      const unavailableUrl = 'https://www.youtube.com/watch?v=invalid_video_id_xyz123';
+
+      await expect(getVideoComments(unavailableUrl, 5, 'top', CONFIG)).rejects.toThrow();
+    }, 30000);
+
+    test('should handle unsupported URLs gracefully', async () => {
+      const unsupportedUrl = 'https://example.com/not-a-video';
+
+      await expect(getVideoComments(unsupportedUrl, 5, 'top', CONFIG)).rejects.toThrow();
+    }, 30000);
+  });
+
+  describe('Comment Fields', () => {
+    test('should include author information when available', async () => {
+      const commentsJson = await getVideoComments(testUrl, 5, 'top', CONFIG);
+      const data: CommentsResponse = JSON.parse(commentsJson);
+
+      if (data.comments.length > 0) {
+        const comment = data.comments[0];
+
+        // Author fields
+        if (comment.author !== undefined) {
+          expect(typeof comment.author).toBe('string');
+        }
+        if (comment.author_id !== undefined) {
+          expect(typeof comment.author_id).toBe('string');
+        }
+      }
+    }, 60000);
+
+    test('should include engagement metrics when available', async () => {
+      const commentsJson = await getVideoComments(testUrl, 5, 'top', CONFIG);
+      const data: CommentsResponse = JSON.parse(commentsJson);
+
+      if (data.comments.length > 0) {
+        // At least one top comment should have like_count
+        const hasLikes = data.comments.some(c =>
+          c.like_count !== undefined && typeof c.like_count === 'number'
+        );
+        // This is optional - some comments may not have likes
+        expect(hasLikes || data.comments.length > 0).toBe(true);
+      }
+    }, 60000);
+
+    test('should handle boolean flags correctly', async () => {
+      const commentsJson = await getVideoComments(testUrl, 10, 'top', CONFIG);
+      const data: CommentsResponse = JSON.parse(commentsJson);
+
+      for (const comment of data.comments) {
+        // Boolean flags should be boolean or undefined
+        if (comment.is_pinned !== undefined) {
+          expect(typeof comment.is_pinned).toBe('boolean');
+        }
+        if (comment.author_is_uploader !== undefined) {
+          expect(typeof comment.author_is_uploader).toBe('boolean');
+        }
+        if (comment.author_is_verified !== undefined) {
+          expect(typeof comment.author_is_verified).toBe('boolean');
+        }
+      }
+    }, 60000);
+  });
+});

src/__tests__/config.test.ts

@@ -0,0 +1,179 @@
+// @ts-nocheck
+// @jest-environment node
+import { describe, test, expect, beforeEach, afterEach, jest } from '@jest/globals';
+import * as fs from 'fs';
+import * as path from 'path';
+import * as os from 'os';
+
+// Store original env
+const originalEnv = { ...process.env };
+
+describe('Cookie Configuration', () => {
+  beforeEach(() => {
+    // Reset environment before each test
+    process.env = { ...originalEnv };
+    // Clear module cache to reload config
+    jest.resetModules();
+  });
+
+  afterEach(() => {
+    process.env = originalEnv;
+  });
+
+  describe('getCookieArgs', () => {
+    test('returns empty array when no cookies configured', async () => {
+      const { getCookieArgs, loadConfig } = await import('../config.js');
+      const config = loadConfig();
+      const args = getCookieArgs(config);
+      expect(args).toEqual([]);
+    });
+
+    test('returns --cookies args when file is configured', async () => {
+      // Create a temporary cookie file
+      const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'cookie-test-'));
+      const cookieFile = path.join(tempDir, 'cookies.txt');
+      fs.writeFileSync(cookieFile, '# Netscape HTTP Cookie File\n');
+
+      process.env.YTDLP_COOKIES_FILE = cookieFile;
+
+      const { getCookieArgs, loadConfig } = await import('../config.js');
+      const config = loadConfig();
+      const args = getCookieArgs(config);
+
+      expect(args).toEqual(['--cookies', cookieFile]);
+
+      // Cleanup
+      fs.rmSync(tempDir, { recursive: true, force: true });
+    });
+
+    test('returns --cookies-from-browser args when browser is configured', async () => {
+      process.env.YTDLP_COOKIES_FROM_BROWSER = 'chrome';
+
+      const { getCookieArgs, loadConfig } = await import('../config.js');
+      const config = loadConfig();
+      const args = getCookieArgs(config);
+
+      expect(args).toEqual(['--cookies-from-browser', 'chrome']);
+    });
+
+    test('file takes precedence over browser', async () => {
+      // Create a temporary cookie file
+      const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'cookie-test-'));
+      const cookieFile = path.join(tempDir, 'cookies.txt');
+      fs.writeFileSync(cookieFile, '# Netscape HTTP Cookie File\n');
+
+      process.env.YTDLP_COOKIES_FILE = cookieFile;
+      process.env.YTDLP_COOKIES_FROM_BROWSER = 'chrome';
+
+      const { getCookieArgs, loadConfig } = await import('../config.js');
+      const config = loadConfig();
+      const args = getCookieArgs(config);
+
+      expect(args).toEqual(['--cookies', cookieFile]);
+
+      // Cleanup
+      fs.rmSync(tempDir, { recursive: true, force: true });
+    });
+
+    test('supports browser with profile', async () => {
+      process.env.YTDLP_COOKIES_FROM_BROWSER = 'chrome:Profile 1';
+
+      const { getCookieArgs, loadConfig } = await import('../config.js');
+      const config = loadConfig();
+      const args = getCookieArgs(config);
+
+      expect(args).toEqual(['--cookies-from-browser', 'chrome:Profile 1']);
+    });
+
+    test('supports browser with container', async () => {
+      process.env.YTDLP_COOKIES_FROM_BROWSER = 'firefox::work';
+
+      const { getCookieArgs, loadConfig } = await import('../config.js');
+      const config = loadConfig();
+      const args = getCookieArgs(config);
+
+      expect(args).toEqual(['--cookies-from-browser', 'firefox::work']);
+    });
+  });
+
+  describe('Cookie Validation', () => {
+    test('clears invalid cookie file path with warning', async () => {
+      const consoleSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+
+      process.env.YTDLP_COOKIES_FILE = '/nonexistent/path/cookies.txt';
+
+      const { loadConfig } = await import('../config.js');
+      const config = loadConfig();
+
+      expect(config.cookies.file).toBeUndefined();
+      expect(consoleSpy).toHaveBeenCalledWith(
+        expect.stringContaining('Cookie file not found')
+      );
+
+      consoleSpy.mockRestore();
+    });
+
+    test('accepts valid browser names', async () => {
+      const validBrowsers = ['brave', 'chrome', 'chromium', 'edge', 'firefox', 'opera', 'safari', 'vivaldi', 'whale'];
+
+      for (const browser of validBrowsers) {
+        jest.resetModules();
+        process.env = { ...originalEnv };
+        process.env.YTDLP_COOKIES_FROM_BROWSER = browser;
+
+        const { loadConfig } = await import('../config.js');
+        const config = loadConfig();
+
+        expect(config.cookies.fromBrowser).toBe(browser);
+      }
+    });
+
+    test('clears invalid browser name with warning', async () => {
+      const consoleSpy = jest.spyOn(console, 'warn').mockImplementation(() => {});
+
+      process.env.YTDLP_COOKIES_FROM_BROWSER = 'invalidbrowser';
+
+      const { loadConfig } = await import('../config.js');
+      const config = loadConfig();
+
+      expect(config.cookies.fromBrowser).toBeUndefined();
+      expect(consoleSpy).toHaveBeenCalledWith(
+        expect.stringContaining('Invalid browser name')
+      );
+
+      consoleSpy.mockRestore();
+    });
+
+    test('accepts valid browser with custom path (Flatpak style)', async () => {
+      // Path format is valid for Flatpak installations
+      process.env.YTDLP_COOKIES_FROM_BROWSER = 'chrome:~/.var/app/com.google.Chrome/';
+
+      const { loadConfig } = await import('../config.js');
+      const config = loadConfig();
+
+      expect(config.cookies.fromBrowser).toBe('chrome:~/.var/app/com.google.Chrome/');
+    });
+
+    test('accepts valid browser with empty profile', async () => {
+      // chrome: is valid (empty profile means default)
+      process.env.YTDLP_COOKIES_FROM_BROWSER = 'chrome:';
+
+      const { loadConfig } = await import('../config.js');
+      const config = loadConfig();
+
+      expect(config.cookies.fromBrowser).toBe('chrome:');
+    });
+  });
+
+  describe('VALID_BROWSERS constant', () => {
+    test('exports valid browsers list', async () => {
+      const { VALID_BROWSERS } = await import('../config.js');
+
+      expect(VALID_BROWSERS).toContain('chrome');
+      expect(VALID_BROWSERS).toContain('firefox');
+      expect(VALID_BROWSERS).toContain('edge');
+      expect(VALID_BROWSERS).toContain('safari');
+      expect(VALID_BROWSERS.length).toBe(9);
+    });
+  });
+});

src/__tests__/index.test.ts

@@ -1,79 +1,56 @@
 // @ts-nocheck
 // @jest-environment node
-import { jest } from '@jest/globals';
-import { describe, test, expect, beforeAll, afterAll, beforeEach } from '@jest/globals';
-import * as path from 'path';
+import { describe, test, expect } from '@jest/globals';
 import * as os from 'os';
+import * as path from 'path';
+import { downloadVideo } from '../modules/video.js';
+import { CONFIG } from '../config.js';
+import * as fs from 'fs';
 
-// 簡化 mock
-jest.mock('spawn-rx', () => ({
-  spawnPromise: jest.fn().mockImplementation(async (cmd, args) => {
-    if (args.includes('--get-filename')) {
-      return 'mock_video.mp4';
-    }
-    return 'Download completed';
-  })
-}));
-jest.mock('rimraf', () => ({
-  rimraf: { sync: jest.fn() }
-}));
-
-import { downloadVideo } from '../index.mts';
+// 設置 Python 環境
+process.env.PYTHONPATH = '';
+process.env.PYTHONHOME = '';
 
 describe('downloadVideo', () => {
-  const mockTimestamp = '2024-03-20_12-30-00';
-  let originalDateToISOString: () => string;
+  const testUrl = 'https://www.youtube.com/watch?v=jNQXAC9IVRw';
+  const testConfig = {
+    ...CONFIG,
+    file: {
+      ...CONFIG.file,
+      downloadsDir: path.join(os.tmpdir(), 'yt-dlp-test-downloads'),
+      tempDirPrefix: 'yt-dlp-test-'
+    }
+  };
 
-  // 全局清理
-  afterAll(done => {
-    // 清理所有計時器
-    jest.useRealTimers();
-    // 確保所有異步操作完成
-    process.nextTick(done);
+  beforeEach(async () => {
+    await fs.promises.mkdir(testConfig.file.downloadsDir, { recursive: true });
   });
 
-  beforeAll(() => {
-    originalDateToISOString = Date.prototype.toISOString;
-    Date.prototype.toISOString = jest.fn(() => '2024-03-20T12:30:00.000Z');
-  });
-
-  afterAll(() => {
-    Date.prototype.toISOString = originalDateToISOString;
-  });
-
-  beforeEach(() => {
-    jest.clearAllMocks();
+  afterEach(async () => {
+    await fs.promises.rm(testConfig.file.downloadsDir, { recursive: true, force: true });
   });
 
   test('downloads video successfully with correct format', async () => {
-    const result = await downloadVideo('https://www.youtube.com/watch?v=dQw4w9WgXcQ');
+    const result = await downloadVideo(testUrl, testConfig);
+    expect(result).toContain('Video successfully downloaded');
     
-    // 驗證基本功能
-    expect(result).toMatch(/Video successfully downloaded as/);
-    expect(result).toContain(mockTimestamp);
-    expect(result).toContain(os.homedir());
-    expect(result).toContain('Downloads');
-  });
-
-  test('handles special characters in video URL', async () => {
-    // 使用有效的視頻 ID，但包含需要編碼的字符
-    const result = await downloadVideo('https://www.youtube.com/watch?v=dQw4w9WgXcQ&title=特殊字符');
-    
-    expect(result).toMatch(/Video successfully downloaded as/);
-    expect(result).toContain(mockTimestamp);
-  });
+    const files = await fs.promises.readdir(testConfig.file.downloadsDir);
+    expect(files.length).toBeGreaterThan(0);
+    expect(files[0]).toMatch(/\.(mp4|webm|mkv)$/);
+  }, 30000);
 
   test('uses correct resolution format', async () => {
-    const resolutions = ['480p', '720p', '1080p', 'best'];
+    const result = await downloadVideo(testUrl, testConfig, '1080p');
+    expect(result).toContain('Video successfully downloaded');
     
-    // 使用 Promise.all 並行執行測試
-    const results = await Promise.all(resolutions.map(resolution => downloadVideo(
-      'https://www.youtube.com/watch?v=dQw4w9WgXcQ',
-      resolution
-    )));
-    
-    results.forEach(result => {
-      expect(result).toMatch(/Video successfully downloaded as/);
-    });
+    const files = await fs.promises.readdir(testConfig.file.downloadsDir);
+    expect(files.length).toBeGreaterThan(0);
+    expect(files[0]).toMatch(/\.(mp4|webm|mkv)$/);
+  }, 30000);
+
+  test('handles invalid URL', async () => {
+    await expect(downloadVideo('invalid-url', testConfig))
+      .rejects
+      .toThrow();
   });
 }); 

src/__tests__/metadata.test.ts

@@ -0,0 +1,193 @@
+// @ts-nocheck
+// @jest-environment node
+import { describe, test, expect, beforeAll } from '@jest/globals';
+import { getVideoMetadata, getVideoMetadataSummary } from '../modules/metadata.js';
+import type { VideoMetadata } from '../modules/metadata.js';
+import { CONFIG } from '../config.js';
+
+// 設置 Python 環境
+process.env.PYTHONPATH = '';
+process.env.PYTHONHOME = '';
+
+describe('Video Metadata Extraction', () => {
+  const testUrl = 'https://www.youtube.com/watch?v=jNQXAC9IVRw';
+
+  describe('getVideoMetadata', () => {
+    test('should extract basic metadata from YouTube video', async () => {
+      const metadataJson = await getVideoMetadata(testUrl);
+      const metadata: VideoMetadata = JSON.parse(metadataJson);
+
+      // 驗證基本字段存在
+      expect(metadata).toHaveProperty('id');
+      expect(metadata).toHaveProperty('title');
+      expect(metadata).toHaveProperty('uploader');
+      expect(metadata).toHaveProperty('duration');
+      expect(metadata.id).toBe('jNQXAC9IVRw');
+      expect(typeof metadata.title).toBe('string');
+      expect(typeof metadata.uploader).toBe('string');
+      expect(typeof metadata.duration).toBe('number');
+    });
+
+    test('should extract specific fields when requested', async () => {
+      const fields = ['id', 'title', 'description', 'channel', 'timestamp'];
+      const metadataJson = await getVideoMetadata(testUrl, fields);
+      const metadata = JSON.parse(metadataJson);
+
+      // 應該只包含請求的字段
+      expect(Object.keys(metadata)).toEqual(expect.arrayContaining(fields.filter(f => metadata[f] !== undefined)));
+      
+      // 不應該包含其他字段（如果它們存在於原始數據中）
+      expect(metadata).not.toHaveProperty('formats');
+      expect(metadata).not.toHaveProperty('thumbnails');
+    });
+
+    test('should handle empty fields array gracefully', async () => {
+      const metadataJson = await getVideoMetadata(testUrl, []);
+      const metadata = JSON.parse(metadataJson);
+      
+      // 空數組應該返回空對象
+      expect(metadata).toEqual({});
+    });
+
+    test('should handle non-existent fields gracefully', async () => {
+      const fields = ['id', 'title', 'non_existent_field', 'another_fake_field'];
+      const metadataJson = await getVideoMetadata(testUrl, fields);
+      const metadata = JSON.parse(metadataJson);
+
+      // 應該包含存在的字段
+      expect(metadata).toHaveProperty('id');
+      expect(metadata).toHaveProperty('title');
+      
+      // 不應該包含不存在的字段
+      expect(metadata).not.toHaveProperty('non_existent_field');
+      expect(metadata).not.toHaveProperty('another_fake_field');
+    });
+
+    test('should throw error for invalid URL', async () => {
+      await expect(getVideoMetadata('invalid-url')).rejects.toThrow();
+      await expect(getVideoMetadata('https://invalid-domain.com/video')).rejects.toThrow();
+    });
+
+    test('should include requested metadata fields from issue #16', async () => {
+      const fields = ['id', 'title', 'description', 'creators', 'timestamp', 'channel', 'channel_id', 'channel_url'];
+      const metadataJson = await getVideoMetadata(testUrl, fields);
+      const metadata = JSON.parse(metadataJson);
+
+      // 驗證 issue #16 中請求的字段
+      expect(metadata).toHaveProperty('id');
+      expect(metadata).toHaveProperty('title');
+      expect(metadata.id).toBe('jNQXAC9IVRw');
+      expect(typeof metadata.title).toBe('string');
+
+      // 這些字段可能存在也可能不存在，取決於視頻
+      if (metadata.description !== undefined) {
+        expect(typeof metadata.description).toBe('string');
+      }
+      if (metadata.creators !== undefined && metadata.creators !== null) {
+        // creators can be an array or a string depending on the video
+        expect(Array.isArray(metadata.creators) || typeof metadata.creators === 'string').toBe(true);
+      }
+      if (metadata.timestamp !== undefined) {
+        expect(typeof metadata.timestamp).toBe('number');
+      }
+      if (metadata.channel !== undefined) {
+        expect(typeof metadata.channel).toBe('string');
+      }
+      if (metadata.channel_id !== undefined) {
+        expect(typeof metadata.channel_id).toBe('string');
+      }
+      if (metadata.channel_url !== undefined) {
+        expect(typeof metadata.channel_url).toBe('string');
+      }
+    });
+  });
+
+  describe('getVideoMetadataSummary', () => {
+    test('should generate human-readable summary', async () => {
+      const summary = await getVideoMetadataSummary(testUrl);
+      
+      expect(typeof summary).toBe('string');
+      expect(summary.length).toBeGreaterThan(0);
+      
+      // 應該包含基本信息
+      expect(summary).toMatch(/Title:/);
+      
+      // 可能包含的其他字段
+      const commonFields = ['Channel:', 'Duration:', 'Views:', 'Upload Date:'];
+      const hasAtLeastOneField = commonFields.some(field => summary.includes(field));
+      expect(hasAtLeastOneField).toBe(true);
+    });
+
+    test('should handle videos with different metadata availability', async () => {
+      const summary = await getVideoMetadataSummary(testUrl);
+      
+      // 摘要應該是有效的字符串
+      expect(typeof summary).toBe('string');
+      expect(summary.trim().length).toBeGreaterThan(0);
+      
+      // 每行應該有意義的格式 (字段: 值) - 但要注意有些標題可能包含特殊字符
+      const lines = summary.split('\n').filter(line => line.trim());
+      expect(lines.length).toBeGreaterThan(0);
+      
+      // 至少應該有一行包含冒號（格式為 "字段: 值"）
+      const hasFormattedLines = lines.some(line => line.includes(':'));
+      expect(hasFormattedLines).toBe(true);
+    }, 30000);
+
+    test('should throw error for invalid URL', async () => {
+      await expect(getVideoMetadataSummary('invalid-url')).rejects.toThrow();
+    }, 30000);
+  });
+
+  describe('Error Handling', () => {
+    test('should provide helpful error message for unavailable video', async () => {
+      const unavailableUrl = 'https://www.youtube.com/watch?v=invalid_video_id_123456789';
+      
+      await expect(getVideoMetadata(unavailableUrl)).rejects.toThrow(/unavailable|private|not available/i);
+    });
+
+    test('should handle network errors gracefully', async () => {
+      // 使用一個應該引起網路錯誤的 URL
+      const badNetworkUrl = 'https://httpstat.us/500';
+      
+      await expect(getVideoMetadata(badNetworkUrl)).rejects.toThrow();
+    });
+
+    test('should handle unsupported URLs', async () => {
+      const unsupportedUrl = 'https://example.com/not-a-video';
+      
+      await expect(getVideoMetadata(unsupportedUrl)).rejects.toThrow();
+    }, 10000);
+  });
+
+  describe('Real-world Integration', () => {
+    test('should work with different video platforms supported by yt-dlp', async () => {
+      // 只測試 YouTube，因為其他平台的可用性可能會變化
+      const youtubeUrl = 'https://www.youtube.com/watch?v=jNQXAC9IVRw';
+      
+      const metadataJson = await getVideoMetadata(youtubeUrl, ['id', 'title', 'extractor']);
+      const metadata = JSON.parse(metadataJson);
+      
+      expect(metadata.extractor).toMatch(/youtube/i);
+      expect(metadata.id).toBe('jNQXAC9IVRw');
+    });
+
+    test('should extract metadata that matches issue #16 requirements', async () => {
+      const requiredFields = ['id', 'title', 'description', 'creators', 'timestamp', 'channel', 'channel_id', 'channel_url'];
+      const metadataJson = await getVideoMetadata(testUrl, requiredFields);
+      const metadata = JSON.parse(metadataJson);
+      
+      // 驗證至少有基本字段
+      expect(metadata).toHaveProperty('id');
+      expect(metadata).toHaveProperty('title');
+      
+      // 記錄實際返回的字段以便調試
+      console.log('Available metadata fields for issue #16:', Object.keys(metadata));
+      
+      // 檢查每個請求的字段是否存在或者有合理的替代
+      const availableFields = Object.keys(metadata);
+      const hasRequiredBasics = availableFields.includes('id') && availableFields.includes('title');
+      expect(hasRequiredBasics).toBe(true);
+    });
+  });
+});

src/__tests__/search.test.ts

@@ -0,0 +1,69 @@
+// @ts-nocheck
+// @jest-environment node
+import { describe, test, expect } from '@jest/globals';
+import { searchVideos } from '../modules/search.js';
+import { CONFIG } from '../config.js';
+
+describe('Search functionality tests', () => {
+
+  describe('searchVideos', () => {
+    test('should successfully search for JavaScript tutorials', async () => {
+      const result = await searchVideos('javascript tutorial', 3, 0, 'markdown', CONFIG);
+
+      expect(result).toContain('Found 3 videos');
+      expect(result).toContain('Channel:');
+      expect(result).toContain('Duration:');
+      expect(result).toContain('URL:');
+      expect(result).toContain('ID:');
+      expect(result).toContain('https://www.youtube.com/watch?v=');
+      expect(result).toContain('You can use any URL to download videos, audio, or subtitles!');
+    }, 30000); // Increase timeout for real network calls
+
+    test('should reject empty search queries', async () => {
+      await expect(searchVideos('', 10, 0, 'markdown', CONFIG)).rejects.toThrow('Search query cannot be empty');
+      await expect(searchVideos('   ', 10, 0, 'markdown', CONFIG)).rejects.toThrow('Search query cannot be empty');
+    });
+
+    test('should validate maxResults parameter range', async () => {
+      await expect(searchVideos('test', 0, 0, 'markdown', CONFIG)).rejects.toThrow('Number of results must be between 1 and 50');
+      await expect(searchVideos('test', 51, 0, 'markdown', CONFIG)).rejects.toThrow('Number of results must be between 1 and 50');
+    });
+
+    test('should handle search with different result counts', async () => {
+      const result1 = await searchVideos('python programming', 1, 0, 'markdown', CONFIG);
+      const result5 = await searchVideos('python programming', 5, 0, 'markdown', CONFIG);
+
+      expect(result1).toContain('Found 1 video');
+      expect(result5).toContain('Found 5 videos');
+
+      // Count number of video entries (each video has a numbered entry)
+      const count1 = (result1.match(/^\d+\./gm) || []).length;
+      const count5 = (result5.match(/^\d+\./gm) || []).length;
+
+      expect(count1).toBe(1);
+      expect(count5).toBe(5);
+    }, 30000);
+
+    test('should return properly formatted results', async () => {
+      const result = await searchVideos('react tutorial', 2, 0, 'markdown', CONFIG);
+
+      // Check for proper formatting
+      expect(result).toMatch(/Found \d+ videos? \(showing \d+\):/);
+      expect(result).toMatch(/\d+\. \*\*.*\*\*/); // Numbered list with bold titles
+      expect(result).toMatch(/📺 Channel: .+/);
+      expect(result).toMatch(/⏱️  Duration: .+/);
+      expect(result).toMatch(/🔗 URL: https:\/\/www\.youtube\.com\/watch\?v=.+/);
+      expect(result).toMatch(/🆔 ID: .+/);
+    }, 30000);
+
+    test('should handle obscure search terms gracefully', async () => {
+      // Using a very specific and unlikely search term
+      const result = await searchVideos('asdfghjklqwertyuiopzxcvbnm12345', 1, 0, 'markdown', CONFIG);
+
+      // Even obscure terms should return some results, as YouTube's search is quite broad
+      // But if no results, it should be handled gracefully
+      expect(typeof result).toBe('string');
+      expect(result.length).toBeGreaterThan(0);
+    }, 30000);
+  });
+}); 

src/__tests__/subtitle.test.ts

@@ -0,0 +1,111 @@
+// @ts-nocheck
+// @jest-environment node
+import { describe, test, expect } from '@jest/globals';
+import * as os from 'os';
+import * as path from 'path';
+import { listSubtitles, downloadSubtitles, downloadTranscript } from '../modules/subtitle.js';
+import { cleanSubtitleToTranscript } from '../modules/utils.js';
+import { CONFIG } from '../config.js';
+import * as fs from 'fs';
+
+describe('Subtitle Functions', () => {
+  const testUrl = 'https://www.youtube.com/watch?v=jNQXAC9IVRw';
+  const testConfig = {
+    ...CONFIG,
+    file: {
+      ...CONFIG.file,
+      downloadsDir: path.join(os.tmpdir(), 'yt-dlp-test-downloads'),
+      tempDirPrefix: 'yt-dlp-test-'
+    }
+  };
+
+  beforeEach(async () => {
+    await fs.promises.mkdir(testConfig.file.downloadsDir, { recursive: true });
+  });
+
+  afterEach(async () => {
+    await fs.promises.rm(testConfig.file.downloadsDir, { recursive: true, force: true });
+  });
+
+  describe('listSubtitles', () => {
+    test('lists available subtitles', async () => {
+      const result = await listSubtitles(testUrl);
+      expect(result).toContain('Language');
+    }, 30000);
+
+    test('handles invalid URL', async () => {
+      await expect(listSubtitles('invalid-url'))
+        .rejects
+        .toThrow();
+    });
+  });
+
+  describe('downloadSubtitles', () => {
+    test('downloads auto-generated subtitles successfully', async () => {
+      const result = await downloadSubtitles(testUrl, 'en', testConfig);
+      expect(result).toContain('WEBVTT');
+    }, 30000);
+
+    test('handles missing language', async () => {
+      await expect(downloadSubtitles(testUrl, 'xx', testConfig))
+        .rejects
+        .toThrow();
+    });
+  });
+
+  describe('downloadTranscript', () => {
+    test('downloads and cleans transcript successfully', async () => {
+      const result = await downloadTranscript(testUrl, 'en', testConfig);
+      expect(typeof result).toBe('string');
+      expect(result.length).toBeGreaterThan(0);
+      expect(result).not.toContain('WEBVTT');
+      expect(result).not.toContain('-->');
+      expect(result).not.toMatch(/^\d+$/m);
+    }, 30000);
+
+    test('handles invalid URL', async () => {
+      await expect(downloadTranscript('invalid-url', 'en', testConfig))
+        .rejects
+        .toThrow();
+    });
+  });
+
+  describe('cleanSubtitleToTranscript', () => {
+    test('cleans SRT content correctly', () => {
+      const srtContent = `1
+00:00:01,000 --> 00:00:03,000
+Hello <i>world</i>
+
+2
+00:00:04,000 --> 00:00:06,000
+This is a test
+
+3
+00:00:07,000 --> 00:00:09,000
+<b>Bold text</b> here`;
+
+      const result = cleanSubtitleToTranscript(srtContent);
+      expect(result).toBe('Hello world This is a test Bold text here');
+    });
+
+    test('handles empty content', () => {
+      const result = cleanSubtitleToTranscript('');
+      expect(result).toBe('');
+    });
+
+    test('removes timestamps and sequence numbers', () => {
+      const srtContent = `1
+00:00:01,000 --> 00:00:03,000
+First line
+
+2
+00:00:04,000 --> 00:00:06,000
+Second line`;
+
+      const result = cleanSubtitleToTranscript(srtContent);
+      expect(result).not.toContain('00:00');
+      expect(result).not.toMatch(/^\d+$/);
+      expect(result).toBe('First line Second line');
+    });
+  });
+}); 

src/__tests__/video.test.ts

@@ -0,0 +1,68 @@
+// @ts-nocheck
+// @jest-environment node
+import { describe, test, expect } from '@jest/globals';
+import * as os from 'os';
+import * as path from 'path';
+import { downloadVideo } from '../modules/video.js';
+import { CONFIG } from '../config.js';
+import * as fs from 'fs';
+
+// 設置 Python 環境
+process.env.PYTHONPATH = '';
+process.env.PYTHONHOME = '';
+
+describe('downloadVideo with trimming', () => {
+  const testUrl = 'https://www.youtube.com/watch?v=jNQXAC9IVRw';
+  const testConfig = {
+    ...CONFIG,
+    file: {
+      ...CONFIG.file,
+      downloadsDir: path.join(os.tmpdir(), 'yt-dlp-test-downloads'),
+      tempDirPrefix: 'yt-dlp-test-'
+    }
+  };
+
+  beforeEach(async () => {
+    await fs.promises.mkdir(testConfig.file.downloadsDir, { recursive: true });
+  });
+
+  afterEach(async () => {
+    await fs.promises.rm(testConfig.file.downloadsDir, { recursive: true, force: true });
+  });
+
+  test('downloads video with start time trimming', async () => {
+    const result = await downloadVideo(testUrl, testConfig, '720p', '00:00:10');
+    expect(result).toContain('Video successfully downloaded');
+    
+    const files = await fs.promises.readdir(testConfig.file.downloadsDir);
+    expect(files.length).toBeGreaterThan(0);
+    expect(files[0]).toMatch(/\.(mp4|webm|mkv)$/);
+  }, 30000);
+
+  test('downloads video with end time trimming', async () => {
+    const result = await downloadVideo(testUrl, testConfig, '720p', undefined, '00:00:20');
+    expect(result).toContain('Video successfully downloaded');
+    
+    const files = await fs.promises.readdir(testConfig.file.downloadsDir);
+    expect(files.length).toBeGreaterThan(0);
+    expect(files[0]).toMatch(/\.(mp4|webm|mkv)$/);
+  }, 30000);
+
+  test('downloads video with both start and end time trimming', async () => {
+    const result = await downloadVideo(testUrl, testConfig, '720p', '00:00:10', '00:00:20');
+    expect(result).toContain('Video successfully downloaded');
+    
+    const files = await fs.promises.readdir(testConfig.file.downloadsDir);
+    expect(files.length).toBeGreaterThan(0);
+    expect(files[0]).toMatch(/\.(mp4|webm|mkv)$/);
+  }, 30000);
+
+  test('downloads video without trimming when no times provided', async () => {
+    const result = await downloadVideo(testUrl, testConfig, '720p');
+    expect(result).toContain('Video successfully downloaded');
+    
+    const files = await fs.promises.readdir(testConfig.file.downloadsDir);
+    expect(files.length).toBeGreaterThan(0);
+    expect(files[0]).toMatch(/\.(mp4|webm|mkv)$/);
+  }, 30000);
+});

src/config.ts

@@ -0,0 +1,329 @@
+import * as os from "os";
+import * as path from "path";
+import * as fs from "fs";
+
+type DeepPartial<T> = {
+  [P in keyof T]?: T[P] extends object ? DeepPartial<T[P]> : T[P];
+};
+
+/**
+ * Valid browser names for cookie extraction
+ */
+export const VALID_BROWSERS = [
+  'brave', 'chrome', 'chromium', 'edge',
+  'firefox', 'opera', 'safari', 'vivaldi', 'whale'
+] as const;
+
+export type ValidBrowser = typeof VALID_BROWSERS[number];
+
+/**
+ * Configuration type definitions
+ */
+export interface Config {
+  // File-related configuration
+  file: {
+    maxFilenameLength: number;
+    downloadsDir: string;
+    tempDirPrefix: string;
+    // Filename processing configuration
+    sanitize: {
+      // Character to replace illegal characters
+      replaceChar: string;
+      // Suffix when truncating filenames
+      truncateSuffix: string;
+      // Regular expression for illegal characters
+      illegalChars: RegExp;
+      // List of reserved names
+      reservedNames: readonly string[];
+    };
+  };
+  // Tool-related configuration
+  tools: {
+    required: readonly string[];
+  };
+  // Download-related configuration
+  download: {
+    defaultResolution: "480p" | "720p" | "1080p" | "best";
+    defaultAudioFormat: "m4a" | "mp3";
+    defaultSubtitleLanguage: string;
+  };
+  // Response limits
+  limits: {
+    characterLimit: number;
+    maxTranscriptLength: number;
+  };
+  // Cookie configuration for authenticated access
+  cookies: {
+    // Path to Netscape format cookie file
+    file?: string;
+    // Browser name and settings (format: BROWSER[:PROFILE][::CONTAINER])
+    fromBrowser?: string;
+  };
+}
+
+/**
+ * Default configuration
+ */
+const defaultConfig: Config = {
+  file: {
+    maxFilenameLength: 50,
+    downloadsDir: path.join(os.homedir(), "Downloads"),
+    tempDirPrefix: "ytdlp-",
+    sanitize: {
+      replaceChar: '_',
+      truncateSuffix: '...',
+      illegalChars: /[<>:"/\\|?*\x00-\x1F]/g,  // Windows illegal characters
+      reservedNames: [
+        'CON', 'PRN', 'AUX', 'NUL', 'COM1', 'COM2', 'COM3', 'COM4',
+        'COM5', 'COM6', 'COM7', 'COM8', 'COM9', 'LPT1', 'LPT2',
+        'LPT3', 'LPT4', 'LPT5', 'LPT6', 'LPT7', 'LPT8', 'LPT9'
+      ]
+    }
+  },
+  tools: {
+    required: ['yt-dlp']
+  },
+  download: {
+    defaultResolution: "720p",
+    defaultAudioFormat: "m4a",
+    defaultSubtitleLanguage: "en"
+  },
+  limits: {
+    characterLimit: 25000,      // Standard MCP character limit
+    maxTranscriptLength: 50000  // Transcripts can be larger
+  },
+  cookies: {
+    file: undefined,
+    fromBrowser: undefined
+  }
+};
+
+/**
+ * Load configuration from environment variables
+ */
+function loadEnvConfig(): DeepPartial<Config> {
+  const envConfig: DeepPartial<Config> = {};
+
+  // File configuration
+  const fileConfig: DeepPartial<Config['file']> = {
+    sanitize: {
+      replaceChar: process.env.YTDLP_SANITIZE_REPLACE_CHAR,
+      truncateSuffix: process.env.YTDLP_SANITIZE_TRUNCATE_SUFFIX,
+      illegalChars: (() => {
+        if (!process.env.YTDLP_SANITIZE_ILLEGAL_CHARS) return undefined;
+        try {
+          return new RegExp(process.env.YTDLP_SANITIZE_ILLEGAL_CHARS);
+        } catch {
+          console.warn('[yt-dlp-mcp] Invalid regex in YTDLP_SANITIZE_ILLEGAL_CHARS, using default');
+          return undefined;
+        }
+      })(),
+      reservedNames: process.env.YTDLP_SANITIZE_RESERVED_NAMES?.split(',')
+    }
+  };
+
+  if (process.env.YTDLP_MAX_FILENAME_LENGTH) {
+    const parsed = parseInt(process.env.YTDLP_MAX_FILENAME_LENGTH, 10);
+    if (!isNaN(parsed) && parsed >= 5) {
+      fileConfig.maxFilenameLength = parsed;
+    } else {
+      console.warn('[yt-dlp-mcp] Invalid YTDLP_MAX_FILENAME_LENGTH, using default');
+    }
+  }
+  if (process.env.YTDLP_DOWNLOADS_DIR) {
+    fileConfig.downloadsDir = process.env.YTDLP_DOWNLOADS_DIR;
+  }
+  if (process.env.YTDLP_TEMP_DIR_PREFIX) {
+    fileConfig.tempDirPrefix = process.env.YTDLP_TEMP_DIR_PREFIX;
+  }
+
+  if (Object.keys(fileConfig).length > 0) {
+    envConfig.file = fileConfig;
+  }
+
+  // Download configuration
+  const downloadConfig: Partial<Config['download']> = {};
+  if (process.env.YTDLP_DEFAULT_RESOLUTION && 
+      ['480p', '720p', '1080p', 'best'].includes(process.env.YTDLP_DEFAULT_RESOLUTION)) {
+    downloadConfig.defaultResolution = process.env.YTDLP_DEFAULT_RESOLUTION as Config['download']['defaultResolution'];
+  }
+  if (process.env.YTDLP_DEFAULT_AUDIO_FORMAT && 
+      ['m4a', 'mp3'].includes(process.env.YTDLP_DEFAULT_AUDIO_FORMAT)) {
+    downloadConfig.defaultAudioFormat = process.env.YTDLP_DEFAULT_AUDIO_FORMAT as Config['download']['defaultAudioFormat'];
+  }
+  if (process.env.YTDLP_DEFAULT_SUBTITLE_LANG) {
+    downloadConfig.defaultSubtitleLanguage = process.env.YTDLP_DEFAULT_SUBTITLE_LANG;
+  }
+  if (Object.keys(downloadConfig).length > 0) {
+    envConfig.download = downloadConfig;
+  }
+
+  // Cookie configuration
+  const cookiesConfig: Partial<Config['cookies']> = {};
+  if (process.env.YTDLP_COOKIES_FILE) {
+    cookiesConfig.file = process.env.YTDLP_COOKIES_FILE;
+  }
+  if (process.env.YTDLP_COOKIES_FROM_BROWSER) {
+    cookiesConfig.fromBrowser = process.env.YTDLP_COOKIES_FROM_BROWSER;
+  }
+  if (Object.keys(cookiesConfig).length > 0) {
+    envConfig.cookies = cookiesConfig;
+  }
+
+  return envConfig;
+}
+
+/**
+ * Validate configuration
+ */
+function validateConfig(config: Config): void {
+  // Validate filename length
+  if (config.file.maxFilenameLength < 5) {
+    throw new Error('maxFilenameLength must be at least 5');
+  }
+
+  // Validate downloads directory
+  if (!config.file.downloadsDir) {
+    throw new Error('downloadsDir must be specified');
+  }
+
+  // Validate temporary directory prefix
+  if (!config.file.tempDirPrefix) {
+    throw new Error('tempDirPrefix must be specified');
+  }
+
+  // Validate default resolution
+  if (!['480p', '720p', '1080p', 'best'].includes(config.download.defaultResolution)) {
+    throw new Error('Invalid defaultResolution');
+  }
+
+  // Validate default audio format
+  if (!['m4a', 'mp3'].includes(config.download.defaultAudioFormat)) {
+    throw new Error('Invalid defaultAudioFormat');
+  }
+
+  // Validate default subtitle language
+  if (!/^[a-z]{2,3}(-[A-Z][a-z]{3})?(-[A-Z]{2})?$/i.test(config.download.defaultSubtitleLanguage)) {
+    throw new Error('Invalid defaultSubtitleLanguage');
+  }
+
+  // Validate cookies (lenient - warnings only)
+  validateCookiesConfig(config);
+}
+
+/**
+ * Validate cookie configuration (lenient - logs warnings but doesn't throw)
+ */
+function validateCookiesConfig(config: Config): void {
+  // Validate cookie file path
+  if (config.cookies.file) {
+    if (!fs.existsSync(config.cookies.file)) {
+      console.warn(`[yt-dlp-mcp] Cookie file not found: ${config.cookies.file}, continuing without cookies`);
+      config.cookies.file = undefined;
+    }
+  }
+
+  // Validate browser name only
+  // Format: BROWSER[:PROFILE_OR_PATH][::CONTAINER]
+  // We only validate browser name; yt-dlp will validate path/container
+  if (config.cookies.fromBrowser) {
+    const browserName = config.cookies.fromBrowser.split(':')[0].toLowerCase();
+
+    if (!VALID_BROWSERS.includes(browserName as ValidBrowser)) {
+      console.warn(`[yt-dlp-mcp] Invalid browser name: ${browserName}. Valid browsers: ${VALID_BROWSERS.join(', ')}`);
+      config.cookies.fromBrowser = undefined;
+    }
+  }
+}
+
+/**
+ * Merge configuration
+ */
+function mergeConfig(base: Config, override: DeepPartial<Config>): Config {
+  return {
+    file: {
+      maxFilenameLength: override.file?.maxFilenameLength || base.file.maxFilenameLength,
+      downloadsDir: override.file?.downloadsDir || base.file.downloadsDir,
+      tempDirPrefix: override.file?.tempDirPrefix || base.file.tempDirPrefix,
+      sanitize: {
+        replaceChar: override.file?.sanitize?.replaceChar || base.file.sanitize.replaceChar,
+        truncateSuffix: override.file?.sanitize?.truncateSuffix || base.file.sanitize.truncateSuffix,
+        illegalChars: (override.file?.sanitize?.illegalChars || base.file.sanitize.illegalChars) as RegExp,
+        reservedNames: (override.file?.sanitize?.reservedNames || base.file.sanitize.reservedNames) as readonly string[]
+      }
+    },
+    tools: {
+      required: (override.tools?.required || base.tools.required) as readonly string[]
+    },
+    download: {
+      defaultResolution: override.download?.defaultResolution || base.download.defaultResolution,
+      defaultAudioFormat: override.download?.defaultAudioFormat || base.download.defaultAudioFormat,
+      defaultSubtitleLanguage: override.download?.defaultSubtitleLanguage || base.download.defaultSubtitleLanguage
+    },
+    limits: {
+      characterLimit: override.limits?.characterLimit || base.limits.characterLimit,
+      maxTranscriptLength: override.limits?.maxTranscriptLength || base.limits.maxTranscriptLength
+    },
+    cookies: {
+      file: override.cookies?.file ?? base.cookies.file,
+      fromBrowser: override.cookies?.fromBrowser ?? base.cookies.fromBrowser
+    }
+  };
+}
+
+/**
+ * Load configuration
+ */
+export function loadConfig(): Config {
+  const envConfig = loadEnvConfig();
+  const config = mergeConfig(defaultConfig, envConfig);
+  validateConfig(config);
+  return config;
+}
+
+/**
+ * Safe filename processing function
+ */
+export function sanitizeFilename(filename: string, config: Config['file']): string {
+  // Remove illegal characters
+  let safe = filename.replace(config.sanitize.illegalChars, config.sanitize.replaceChar);
+  
+  // Check reserved names
+  const basename = path.parse(safe).name.toUpperCase();
+  if (config.sanitize.reservedNames.includes(basename)) {
+    safe = `_${safe}`;
+  }
+  
+  // Handle length limitation
+  if (safe.length > config.maxFilenameLength) {
+    const ext = path.extname(safe);
+    const name = safe.slice(0, config.maxFilenameLength - ext.length - config.sanitize.truncateSuffix.length);
+    safe = `${name}${config.sanitize.truncateSuffix}${ext}`;
+  }
+  
+  return safe;
+}
+
+/**
+ * Get cookie-related yt-dlp arguments
+ * Priority: file > fromBrowser
+ * @param config Configuration object
+ * @returns Array of yt-dlp arguments for cookie handling
+ */
+export function getCookieArgs(config: Config): string[] {
+  // Guard against missing cookies config
+  if (!config.cookies) {
+    return [];
+  }
+  // Cookie file takes precedence over browser extraction
+  if (config.cookies.file) {
+    return ['--cookies', config.cookies.file];
+  }
+  if (config.cookies.fromBrowser) {
+    return ['--cookies-from-browser', config.cookies.fromBrowser];
+  }
+  return [];
+}
+
+// Export current configuration instance
+export const CONFIG = loadConfig(); 

src/modules/audio.ts

@@ -0,0 +1,81 @@
+import { readdirSync } from "fs";
+import * as path from "path";
+import type { Config } from "../config.js";
+import { sanitizeFilename, getCookieArgs } from "../config.js";
+import { _spawnPromise, validateUrl, getFormattedTimestamp, isYouTubeUrl } from "./utils.js";
+
+/**
+ * Downloads audio from a video URL in the best available quality.
+ * 
+ * @param url - The URL of the video to extract audio from
+ * @param config - Configuration object for download settings
+ * @returns Promise resolving to a success message with the downloaded file path
+ * @throws {Error} When URL is invalid or download fails
+ * 
+ * @example
+ * ```typescript
+ * // Download audio with default settings
+ * const result = await downloadAudio('https://youtube.com/watch?v=...');
+ * console.log(result);
+ * 
+ * // Download audio with custom config
+ * const customResult = await downloadAudio('https://youtube.com/watch?v=...', {
+ *   file: {
+ *     downloadsDir: '/custom/path',
+ *     // ... other config options
+ *   }
+ * });
+ * console.log(customResult);
+ * ```
+ */
+export async function downloadAudio(url: string, config: Config): Promise<string> {
+  const timestamp = getFormattedTimestamp();
+
+  if (!validateUrl(url)) {
+    throw new Error("Invalid or unsupported URL format");
+  }
+
+  try {
+    const outputTemplate = path.join(
+      config.file.downloadsDir,
+      sanitizeFilename(`%(title)s [%(id)s] ${timestamp}`, config.file) + '.%(ext)s'
+    );
+
+    const format = isYouTubeUrl(url)
+      ? "140/bestaudio[ext=m4a]/bestaudio"
+      : "bestaudio[ext=m4a]/bestaudio[ext=mp3]/bestaudio";
+
+    await _spawnPromise("yt-dlp", [
+      "--ignore-config",
+      "--no-check-certificate",
+      "--verbose",
+      "--progress",
+      "--newline",
+      "--no-mtime",
+      "-f", format,
+      "--output", outputTemplate,
+      ...getCookieArgs(config),
+      url
+    ]);
+
+    const files = readdirSync(config.file.downloadsDir);
+    const downloadedFile = files.find(file => file.includes(timestamp));
+    if (!downloadedFile) {
+      throw new Error("Download completed but file not found. Check Downloads folder permissions.");
+    }
+    return `Audio successfully downloaded as "${downloadedFile}" to ${config.file.downloadsDir}`;
+  } catch (error) {
+    if (error instanceof Error) {
+      if (error.message.includes("Unsupported URL") || error.message.includes("extractor")) {
+        throw new Error(`Unsupported platform or video URL: ${url}. Ensure the URL is from a supported platform.`);
+      }
+      if (error.message.includes("Video unavailable") || error.message.includes("private")) {
+        throw new Error(`Video is unavailable or private: ${url}. Check the URL and video privacy settings.`);
+      }
+      if (error.message.includes("network") || error.message.includes("Connection")) {
+        throw new Error("Network error during audio extraction. Check your internet connection and retry.");
+      }
+    }
+    throw error;
+  }
+} 

src/modules/comments.ts

@@ -0,0 +1,283 @@
+import type { Config } from "../config.js";
+import { getCookieArgs } from "../config.js";
+import {
+  _spawnPromise,
+  validateUrl
+} from "./utils.js";
+
+/**
+ * Represents a single comment on a video
+ */
+export interface Comment {
+  /** Unique comment identifier */
+  id?: string;
+  /** Comment text content */
+  text?: string;
+  /** Comment author name */
+  author?: string;
+  /** Comment author channel ID */
+  author_id?: string;
+  /** Comment author channel URL */
+  author_url?: string;
+  /** Whether the author is the video uploader */
+  author_is_uploader?: boolean;
+  /** Whether author is verified */
+  author_is_verified?: boolean;
+  /** Comment like count */
+  like_count?: number;
+  /** Whether comment is pinned */
+  is_pinned?: boolean;
+  /** Whether comment is marked as favorite by uploader */
+  is_favorited?: boolean;
+  /** Parent comment ID (for replies) */
+  parent?: string;
+  /** Unix timestamp of comment */
+  timestamp?: number;
+  /** Human-readable time ago string */
+  time_text?: string;
+  /** Additional fields that might be present */
+  [key: string]: unknown;
+}
+
+/**
+ * Response structure for video comments
+ */
+export interface CommentsResponse {
+  /** Total number of comments returned */
+  count: number;
+  /** Whether there are more comments available */
+  has_more: boolean;
+  /** Array of comment objects */
+  comments: Comment[];
+  /** Truncation indicator */
+  _truncated?: boolean;
+  /** Truncation message */
+  _message?: string;
+}
+
+/**
+ * Sort order for comments
+ */
+export type CommentSortOrder = "top" | "new";
+
+/**
+ * Extract video comments using yt-dlp.
+ * Uses yt-dlp's --write-comments and --dump-json flags to get comments.
+ *
+ * @param url - The URL of the video to extract comments from
+ * @param maxComments - Maximum number of comments to retrieve (default: 20)
+ * @param sortOrder - Sort order: "top" for most liked, "new" for newest (default: "top")
+ * @param config - Configuration object
+ * @returns Promise resolving to JSON string with comments data
+ * @throws {Error} When URL is invalid or comment extraction fails
+ *
+ * @example
+ * ```typescript
+ * // Get top 20 comments
+ * const comments = await getVideoComments('https://youtube.com/watch?v=...');
+ * console.log(comments);
+ *
+ * // Get newest 50 comments
+ * const newComments = await getVideoComments(
+ *   'https://youtube.com/watch?v=...',
+ *   50,
+ *   'new'
+ * );
+ * ```
+ */
+export async function getVideoComments(
+  url: string,
+  maxComments: number = 20,
+  sortOrder: CommentSortOrder = "top",
+  _config?: Config
+): Promise<string> {
+  // Validate the URL
+  if (!validateUrl(url)) {
+    throw new Error("Invalid or unsupported URL format");
+  }
+
+  const args = [
+    "--dump-json",
+    "--no-warnings",
+    "--no-check-certificate",
+    "--write-comments",
+    "--extractor-args", `youtube:comment_sort=${sortOrder};max_comments=${maxComments},all,all`,
+    "--skip-download",
+    ...(_config ? getCookieArgs(_config) : []),
+    url
+  ];
+
+  try {
+    // Execute yt-dlp to get metadata with comments
+    const output = await _spawnPromise("yt-dlp", args);
+
+    // Parse the JSON output
+    const metadata = JSON.parse(output);
+
+    // Extract comments from metadata
+    const rawComments: Comment[] = metadata.comments || [];
+
+    // Limit to maxComments
+    const comments = rawComments.slice(0, maxComments);
+
+    // Build response
+    const response: CommentsResponse = {
+      count: comments.length,
+      has_more: rawComments.length > maxComments,
+      comments: comments.map(comment => ({
+        id: comment.id,
+        text: comment.text,
+        author: comment.author,
+        author_id: comment.author_id,
+        author_url: comment.author_url,
+        author_is_uploader: comment.author_is_uploader,
+        author_is_verified: comment.author_is_verified,
+        like_count: comment.like_count,
+        is_pinned: comment.is_pinned,
+        is_favorited: comment.is_favorited,
+        parent: comment.parent,
+        timestamp: comment.timestamp,
+        time_text: comment.time_text
+      }))
+    };
+
+    let result = JSON.stringify(response, null, 2);
+
+    // Check character limit
+    if (_config && result.length > _config.limits.characterLimit) {
+      // Reduce comments to fit within limit
+      let truncatedComments = [...response.comments];
+
+      while (result.length > _config.limits.characterLimit && truncatedComments.length > 1) {
+        truncatedComments = truncatedComments.slice(0, -1);
+        const truncatedResponse: CommentsResponse = {
+          count: truncatedComments.length,
+          has_more: true,
+          comments: truncatedComments,
+          _truncated: true,
+          _message: `Response truncated to ${truncatedComments.length} comments due to size limits. Use smaller maxComments value.`
+        };
+        result = JSON.stringify(truncatedResponse, null, 2);
+      }
+    }
+
+    return result;
+
+  } catch (error) {
+    if (error instanceof Error) {
+      // Handle common yt-dlp errors with actionable messages
+      if (error.message.includes("Video unavailable") || error.message.includes("private")) {
+        throw new Error(`Video is unavailable or private: ${url}. Check the URL and video privacy settings.`);
+      } else if (error.message.includes("Unsupported URL") || error.message.includes("extractor")) {
+        throw new Error(`Unsupported platform or video URL: ${url}. Comments extraction is primarily supported for YouTube.`);
+      } else if (error.message.includes("network") || error.message.includes("Connection")) {
+        throw new Error("Network error while extracting comments. Check your internet connection and retry.");
+      } else if (error.message.includes("comments are disabled") || error.message.includes("Comments are turned off")) {
+        throw new Error(`Comments are disabled for this video: ${url}`);
+      } else if (error.message.includes("Sign in") || error.message.includes("age")) {
+        throw new Error(`This video requires authentication to view comments. Configure cookies in your settings.`);
+      } else {
+        throw new Error(`Failed to extract video comments: ${error.message}. Verify the URL is correct.`);
+      }
+    }
+    throw new Error(`Failed to extract video comments from ${url}`);
+  }
+}
+
+/**
+ * Get a human-readable summary of video comments.
+ * This is useful for quick overview without overwhelming JSON output.
+ *
+ * @param url - The URL of the video to extract comments from
+ * @param maxComments - Maximum number of comments to include (default: 10)
+ * @param config - Configuration object
+ * @returns Promise resolving to a formatted summary string
+ * @throws {Error} When URL is invalid or comment extraction fails
+ *
+ * @example
+ * ```typescript
+ * const summary = await getVideoCommentsSummary('https://youtube.com/watch?v=...');
+ * console.log(summary);
+ * // Output:
+ * // Video Comments (10 shown)
+ * // ─────────────────────────
+ * //
+ * // 👤 John Doe (2 days ago) ❤️ 1,234 likes
+ * // This is an awesome video!
+ * //
+ * // 👤 Jane Smith (1 week ago) ❤️ 567 likes
+ * // Great content, keep it up!
+ * ```
+ */
+export async function getVideoCommentsSummary(
+  url: string,
+  maxComments: number = 10,
+  _config?: Config
+): Promise<string> {
+  try {
+    // Get the comments
+    const commentsJson = await getVideoComments(url, maxComments, "top", _config);
+    const data: CommentsResponse = JSON.parse(commentsJson);
+
+    // Format comments into a readable summary
+    const lines: string[] = [];
+
+    lines.push(`Video Comments (${data.count} shown)`);
+    lines.push('─'.repeat(30));
+    lines.push('');
+
+    for (const comment of data.comments) {
+      // Build author line with indicators
+      let authorLine = `Author: ${comment.author || 'Unknown'}`;
+      if (comment.author_is_uploader) {
+        authorLine += ' [UPLOADER]';
+      }
+      if (comment.author_is_verified) {
+        authorLine += ' [VERIFIED]';
+      }
+      if (comment.is_pinned) {
+        authorLine += ' [PINNED]';
+      }
+
+      // Time info
+      if (comment.time_text) {
+        authorLine += ` (${comment.time_text})`;
+      }
+
+      // Likes
+      if (comment.like_count !== undefined && comment.like_count > 0) {
+        authorLine += ` - ${comment.like_count.toLocaleString()} likes`;
+      }
+
+      lines.push(authorLine);
+
+      // Comment text (truncate if too long)
+      if (comment.text) {
+        const text = comment.text.length > 300
+          ? comment.text.substring(0, 300) + '...'
+          : comment.text;
+        lines.push(text);
+      }
+
+      // Note if this is a reply
+      if (comment.parent && comment.parent !== 'root') {
+        lines.push(`(Reply to comment ${comment.parent})`);
+      }
+
+      lines.push('');
+    }
+
+    if (data.has_more) {
+      lines.push('---');
+      lines.push('More comments available. Increase maxComments to see more.');
+    }
+
+    return lines.join('\n');
+  } catch (error) {
+    // Re-throw errors from getVideoComments with context
+    if (error instanceof Error) {
+      throw error;
+    }
+    throw new Error(`Failed to generate comments summary for ${url}`);
+  }
+}

src/modules/metadata.ts

@@ -0,0 +1,345 @@
+import type { Config } from "../config.js";
+import { getCookieArgs } from "../config.js";
+import {
+  _spawnPromise,
+  validateUrl
+} from "./utils.js";
+
+/**
+ * Video metadata interface containing all fields that can be extracted
+ */
+export interface VideoMetadata {
+  // Basic video information
+  id?: string;
+  title?: string;
+  fulltitle?: string;
+  description?: string;
+  alt_title?: string;
+  display_id?: string;
+  
+  // Creator/uploader information
+  uploader?: string;
+  uploader_id?: string;
+  uploader_url?: string;
+  creators?: string[];
+  creator?: string;
+  
+  // Channel information
+  channel?: string;
+  channel_id?: string;
+  channel_url?: string;
+  channel_follower_count?: number;
+  channel_is_verified?: boolean;
+  
+  // Timestamps and dates
+  timestamp?: number;
+  upload_date?: string;
+  release_timestamp?: number;
+  release_date?: string;
+  release_year?: number;
+  modified_timestamp?: number;
+  modified_date?: string;
+  
+  // Video properties
+  duration?: number;
+  duration_string?: string;
+  view_count?: number;
+  concurrent_view_count?: number;
+  like_count?: number;
+  dislike_count?: number;
+  repost_count?: number;
+  average_rating?: number;
+  comment_count?: number;
+  age_limit?: number;
+  
+  // Content classification
+  live_status?: string;
+  is_live?: boolean;
+  was_live?: boolean;
+  playable_in_embed?: string;
+  availability?: string;
+  media_type?: string;
+  
+  // Playlist information
+  playlist_id?: string;
+  playlist_title?: string;
+  playlist?: string;
+  playlist_count?: number;
+  playlist_index?: number;
+  playlist_autonumber?: number;
+  playlist_uploader?: string;
+  playlist_uploader_id?: string;
+  playlist_channel?: string;
+  playlist_channel_id?: string;
+  
+  // URLs and technical info
+  webpage_url?: string;
+  webpage_url_domain?: string;
+  webpage_url_basename?: string;
+  original_url?: string;
+  filename?: string;
+  ext?: string;
+  
+  // Content metadata
+  categories?: string[];
+  tags?: string[];
+  cast?: string[];
+  location?: string;
+  license?: string;
+  
+  // Series/episode information
+  series?: string;
+  series_id?: string;
+  season?: string;
+  season_number?: number;
+  season_id?: string;
+  episode?: string;
+  episode_number?: number;
+  episode_id?: string;
+  
+  // Music/track information
+  track?: string;
+  track_number?: number;
+  track_id?: string;
+  artists?: string[];
+  artist?: string;
+  genres?: string[];
+  genre?: string;
+  composers?: string[];
+  composer?: string;
+  album?: string;
+  album_type?: string;
+  album_artists?: string[];
+  album_artist?: string;
+  disc_number?: number;
+  
+  // Technical metadata
+  extractor?: string;
+  epoch?: number;
+  
+  // Additional fields that might be present
+  [key: string]: unknown;
+}
+
+/**
+ * Extract video metadata without downloading the actual video content.
+ * Uses yt-dlp's --dump-json flag to get comprehensive metadata.
+ *
+ * @param url - The URL of the video to extract metadata from
+ * @param fields - Optional array of specific fields to extract. If not provided, returns all available metadata
+ * @param config - Configuration object (currently unused but kept for consistency)
+ * @returns Promise resolving to formatted metadata string or JSON object
+ * @throws {Error} When URL is invalid or metadata extraction fails
+ *
+ * @example
+ * ```typescript
+ * // Get all metadata
+ * const metadata = await getVideoMetadata('https://youtube.com/watch?v=...');
+ * console.log(metadata);
+ *
+ * // Get specific fields only
+ * const specificData = await getVideoMetadata(
+ *   'https://youtube.com/watch?v=...',
+ *   ['id', 'title', 'description', 'channel']
+ * );
+ * console.log(specificData);
+ * ```
+ */
+export async function getVideoMetadata(
+  url: string,
+  fields?: string[],
+  _config?: Config
+): Promise<string> {
+  // Validate the URL
+  if (!validateUrl(url)) {
+    throw new Error("Invalid or unsupported URL format");
+  }
+
+  const args = [
+    "--dump-json",
+    "--no-warnings",
+    "--no-check-certificate",
+    ...(_config ? getCookieArgs(_config) : []),
+    url
+  ];
+
+  try {
+    // Execute yt-dlp to get metadata
+    const output = await _spawnPromise("yt-dlp", args);
+
+    // Parse the JSON output
+    const metadata: VideoMetadata = JSON.parse(output);
+
+    // If specific fields are requested, filter the metadata
+    if (fields !== undefined && fields.length >= 0) {
+      const filteredMetadata: Partial<VideoMetadata> & { _truncated?: boolean; _message?: string } = {};
+
+      for (const field of fields) {
+        if (metadata.hasOwnProperty(field)) {
+          filteredMetadata[field as keyof VideoMetadata] = metadata[field as keyof VideoMetadata];
+        }
+      }
+
+      let result = JSON.stringify(filteredMetadata, null, 2);
+
+      // Check character limit
+      if (_config && result.length > _config.limits.characterLimit) {
+        // Add truncation info inside JSON before truncating
+        filteredMetadata._truncated = true;
+        filteredMetadata._message = "Response truncated. Specify fewer fields to see complete data.";
+        result = JSON.stringify(filteredMetadata, null, 2);
+
+        // If still too long, truncate the string content
+        if (result.length > _config.limits.characterLimit) {
+          result = result.substring(0, _config.limits.characterLimit) + '\n... }';
+        }
+      }
+
+      return result;
+    }
+
+    // Return formatted JSON string with all metadata
+    let result = JSON.stringify(metadata, null, 2);
+
+    // Check character limit for full metadata
+    if (_config && result.length > _config.limits.characterLimit) {
+      // Try to return essential fields only
+      const essentialFields = ['id', 'title', 'description', 'channel', 'channel_id', 'uploader',
+                               'duration', 'duration_string', 'view_count', 'like_count',
+                               'upload_date', 'tags', 'categories', 'webpage_url'];
+      const essentialMetadata: Partial<VideoMetadata> & { _truncated?: boolean; _message?: string } = {};
+
+      for (const field of essentialFields) {
+        if (metadata.hasOwnProperty(field)) {
+          essentialMetadata[field as keyof VideoMetadata] = metadata[field as keyof VideoMetadata];
+        }
+      }
+
+      // Add truncation info inside the JSON object
+      essentialMetadata._truncated = true;
+      essentialMetadata._message = 'Full metadata truncated to essential fields. Use the "fields" parameter to request specific fields.';
+
+      result = JSON.stringify(essentialMetadata, null, 2);
+    }
+
+    return result;
+
+  } catch (error) {
+    if (error instanceof Error) {
+      // Handle common yt-dlp errors with actionable messages
+      if (error.message.includes("Video unavailable") || error.message.includes("private")) {
+        throw new Error(`Video is unavailable or private: ${url}. Check the URL and video privacy settings.`);
+      } else if (error.message.includes("Unsupported URL") || error.message.includes("extractor")) {
+        throw new Error(`Unsupported platform or video URL: ${url}. Ensure the URL is from a supported platform like YouTube.`);
+      } else if (error.message.includes("network") || error.message.includes("Connection")) {
+        throw new Error("Network error while extracting metadata. Check your internet connection and retry.");
+      } else {
+        throw new Error(`Failed to extract video metadata: ${error.message}. Verify the URL is correct.`);
+      }
+    }
+    throw new Error(`Failed to extract video metadata from ${url}`);
+  }
+}
+
+/**
+ * Get a human-readable summary of key video metadata fields.
+ * This is useful for quick overview without overwhelming JSON output.
+ *
+ * @param url - The URL of the video to extract metadata from
+ * @param config - Configuration object (currently unused but kept for consistency)
+ * @returns Promise resolving to a formatted summary string
+ * @throws {Error} When URL is invalid or metadata extraction fails
+ *
+ * @example
+ * ```typescript
+ * const summary = await getVideoMetadataSummary('https://youtube.com/watch?v=...');
+ * console.log(summary);
+ * // Output:
+ * // Title: Example Video Title
+ * // Channel: Example Channel
+ * // Duration: 10:30
+ * // Views: 1,234,567
+ * // Upload Date: 2023-12-01
+ * // Description: This is an example video...
+ * ```
+ */
+export async function getVideoMetadataSummary(
+  url: string,
+  _config?: Config
+): Promise<string> {
+  try {
+    // Get the full metadata first
+    const metadataJson = await getVideoMetadata(url, undefined, _config);
+    const metadata: VideoMetadata = JSON.parse(metadataJson);
+
+    // Format key fields into a readable summary
+    const lines: string[] = [];
+  
+  if (metadata.title) {
+    lines.push(`Title: ${metadata.title}`);
+  }
+  
+  if (metadata.channel) {
+    lines.push(`Channel: ${metadata.channel}`);
+  }
+  
+  if (metadata.uploader && metadata.uploader !== metadata.channel) {
+    lines.push(`Uploader: ${metadata.uploader}`);
+  }
+  
+  if (metadata.duration_string) {
+    lines.push(`Duration: ${metadata.duration_string}`);
+  } else if (metadata.duration) {
+    const hours = Math.floor(metadata.duration / 3600);
+    const minutes = Math.floor((metadata.duration % 3600) / 60);
+    const seconds = metadata.duration % 60;
+    const durationStr = hours > 0 
+      ? `${hours}:${minutes.toString().padStart(2, '0')}:${seconds.toString().padStart(2, '0')}`
+      : `${minutes}:${seconds.toString().padStart(2, '0')}`;
+    lines.push(`Duration: ${durationStr}`);
+  }
+  
+  if (metadata.view_count !== undefined) {
+    lines.push(`Views: ${metadata.view_count.toLocaleString()}`);
+  }
+  
+  if (metadata.like_count !== undefined) {
+    lines.push(`Likes: ${metadata.like_count.toLocaleString()}`);
+  }
+  
+  if (metadata.upload_date) {
+    // Format YYYYMMDD to YYYY-MM-DD
+    const dateStr = metadata.upload_date;
+    if (dateStr.length === 8) {
+      const formatted = `${dateStr.substring(0, 4)}-${dateStr.substring(4, 6)}-${dateStr.substring(6, 8)}`;
+      lines.push(`Upload Date: ${formatted}`);
+    } else {
+      lines.push(`Upload Date: ${dateStr}`);
+    }
+  }
+  
+  if (metadata.live_status && metadata.live_status !== 'not_live') {
+    lines.push(`Status: ${metadata.live_status.replace('_', ' ')}`);
+  }
+  
+  if (metadata.tags && metadata.tags.length > 0) {
+    lines.push(`Tags: ${metadata.tags.slice(0, 5).join(', ')}${metadata.tags.length > 5 ? '...' : ''}`);
+  }
+  
+  if (metadata.description) {
+    // Truncate description to first 200 characters
+    const desc = metadata.description.length > 200
+      ? metadata.description.substring(0, 200) + '...'
+      : metadata.description;
+    lines.push(`Description: ${desc}`);
+  }
+
+  return lines.join('\n');
+  } catch (error) {
+    // Re-throw errors from getVideoMetadata with context
+    if (error instanceof Error) {
+      throw error;
+    }
+    throw new Error(`Failed to generate metadata summary for ${url}`);
+  }
+}

src/modules/search.ts

@@ -0,0 +1,255 @@
+import { _spawnPromise } from "./utils.js";
+import type { Config } from "../config.js";
+import { getCookieArgs } from "../config.js";
+
+/**
+ * Upload date filter type
+ */
+export type UploadDateFilter = "hour" | "today" | "week" | "month" | "year";
+
+/**
+ * YouTube search result interface
+ */
+export interface SearchResult {
+  title: string;
+  id: string;
+  url: string;
+  uploader?: string;
+  duration?: string;
+  viewCount?: string;
+  uploadDate?: string;
+}
+
+/**
+ * Map upload date filter to YouTube's sp parameter
+ * These are base64-encoded protobuf parameters
+ */
+const UPLOAD_DATE_FILTER_MAP: Record<UploadDateFilter, string> = {
+  hour: "EgIIAQ%3D%3D",   // Last hour
+  today: "EgIIAg%3D%3D",  // Today
+  week: "EgIIAw%3D%3D",   // This week
+  month: "EgIIBA%3D%3D",  // This month
+  year: "EgIIBQ%3D%3D",   // This year
+};
+
+/**
+ * Search YouTube videos
+ * @param query Search keywords
+ * @param maxResults Maximum number of results (1-50)
+ * @param offset Number of results to skip for pagination
+ * @param responseFormat Output format ('json' or 'markdown')
+ * @param config Configuration object
+ * @param uploadDateFilter Optional filter by upload date
+ * @returns Search results formatted as string
+ */
+export async function searchVideos(
+  query: string,
+  maxResults: number = 10,
+  offset: number = 0,
+  responseFormat: "json" | "markdown" = "markdown",
+  config: Config,
+  uploadDateFilter?: UploadDateFilter
+): Promise<string> {
+  // Validate parameters
+  if (!query || query.trim().length === 0) {
+    throw new Error("Search query cannot be empty");
+  }
+
+  if (maxResults < 1 || maxResults > 50) {
+    throw new Error("Number of results must be between 1 and 50");
+  }
+
+  if (offset < 0) {
+    throw new Error("Offset cannot be negative");
+  }
+
+  const cleanQuery = query.trim();
+  // Request more results to support offset
+  const totalToFetch = maxResults + offset;
+
+  try {
+    let args: string[];
+
+    if (uploadDateFilter && UPLOAD_DATE_FILTER_MAP[uploadDateFilter]) {
+      // Use YouTube URL with sp parameter for date filtering
+      const encodedQuery = encodeURIComponent(cleanQuery);
+      const spParam = UPLOAD_DATE_FILTER_MAP[uploadDateFilter];
+      const searchUrl = `https://www.youtube.com/results?search_query=${encodedQuery}&sp=${spParam}`;
+
+      args = [
+        searchUrl,
+        "--flat-playlist",
+        "--print", "title",
+        "--print", "id",
+        "--print", "uploader",
+        "--print", "duration",
+        "--no-download",
+        "--quiet",
+        "--playlist-end", String(totalToFetch),
+        ...getCookieArgs(config)
+      ];
+    } else {
+      // Use ytsearch prefix for regular search
+      const searchQuery = `ytsearch${totalToFetch}:${cleanQuery}`;
+      args = [
+        searchQuery,
+        "--print", "title",
+        "--print", "id",
+        "--print", "uploader",
+        "--print", "duration",
+        "--no-download",
+        "--quiet",
+        ...getCookieArgs(config)
+      ];
+    }
+
+    const result = await _spawnPromise(config.tools.required[0], args);
+    
+    if (!result || result.trim().length === 0) {
+      return "No videos found";
+    }
+
+    // Parse results
+    const lines = result.trim().split('\n');
+    const allResults: SearchResult[] = [];
+
+    // Each video has 4 lines of data: title, id, uploader, duration
+    for (let i = 0; i < lines.length; i += 4) {
+      if (i + 3 < lines.length) {
+        const title = lines[i]?.trim();
+        const id = lines[i + 1]?.trim();
+        const uploader = lines[i + 2]?.trim();
+        const duration = lines[i + 3]?.trim();
+
+        if (title && id) {
+          const url = `https://www.youtube.com/watch?v=${id}`;
+          allResults.push({
+            title,
+            id,
+            url,
+            uploader: uploader || "Unknown",
+            duration: duration || "Unknown"
+          });
+        }
+      }
+    }
+
+    // Apply offset and limit
+    const paginatedResults = allResults.slice(offset, offset + maxResults);
+    const hasMore = allResults.length > offset + maxResults;
+
+    if (paginatedResults.length === 0) {
+      return "No videos found";
+    }
+
+    // Format output based on response format
+    if (responseFormat === "json") {
+      const response = {
+        total: allResults.length,
+        count: paginatedResults.length,
+        offset: offset,
+        videos: paginatedResults,
+        has_more: hasMore,
+        ...(hasMore && { next_offset: offset + maxResults }),
+        ...(uploadDateFilter && { upload_date_filter: uploadDateFilter })
+      };
+
+      let output = JSON.stringify(response, null, 2);
+
+      // Check character limit
+      if (output.length > config.limits.characterLimit) {
+        // Truncate videos array
+        const truncatedCount = Math.ceil(paginatedResults.length / 2);
+        const truncatedResponse = {
+          ...response,
+          count: truncatedCount,
+          videos: paginatedResults.slice(0, truncatedCount),
+          truncated: true,
+          truncation_message: `Response truncated from ${paginatedResults.length} to ${truncatedCount} results. Use offset parameter or reduce maxResults to see more.`
+        };
+        output = JSON.stringify(truncatedResponse, null, 2);
+      }
+
+      return output;
+    } else {
+      // Markdown format
+      let output = `Found ${allResults.length} video${allResults.length > 1 ? 's' : ''} (showing ${paginatedResults.length})`;
+      if (uploadDateFilter) {
+        const filterLabels: Record<UploadDateFilter, string> = {
+          hour: "last hour",
+          today: "today",
+          week: "this week",
+          month: "this month",
+          year: "this year"
+        };
+        output += ` from ${filterLabels[uploadDateFilter]}`;
+      }
+      output += `:\n\n`;
+
+      paginatedResults.forEach((video, index) => {
+        output += `${offset + index + 1}. **${video.title}**\n`;
+        output += `   📺 Channel: ${video.uploader}\n`;
+        output += `   ⏱️  Duration: ${video.duration}\n`;
+        output += `   🔗 URL: ${video.url}\n`;
+        output += `   🆔 ID: ${video.id}\n\n`;
+      });
+
+      // Add pagination info
+      if (offset > 0 || hasMore) {
+        output += `\n📊 Pagination: Showing results ${offset + 1}-${offset + paginatedResults.length} of ${allResults.length}`;
+        if (hasMore) {
+          output += ` (${allResults.length - offset - paginatedResults.length} more available)`;
+        }
+        output += '\n';
+      }
+
+      output += "\n💡 You can use any URL to download videos, audio, or subtitles!";
+
+      // Check character limit
+      if (output.length > config.limits.characterLimit) {
+        output = output.substring(0, config.limits.characterLimit);
+        output += "\n\n⚠️ Response truncated. Use offset parameter or reduce maxResults to see more results.";
+      }
+
+      return output;
+    }
+
+  } catch (error) {
+    if (error instanceof Error) {
+      // Provide more actionable error messages
+      if (error.message.includes("network") || error.message.includes("Network")) {
+        throw new Error("Network error while searching. Check your internet connection and retry.");
+      }
+      if (error.message.includes("429") || error.message.includes("rate limit")) {
+        throw new Error("YouTube rate limit exceeded. Wait 60 seconds before searching again.");
+      }
+      throw new Error(`Search failed: ${error.message}. Try a different query or reduce maxResults.`);
+    }
+    throw new Error(`Error searching videos: ${String(error)}`);
+  }
+}
+
+/**
+ * Search videos on specific platform (future expansion feature)
+ * @param query Search keywords
+ * @param platform Platform name ('youtube', 'bilibili', etc.)
+ * @param maxResults Maximum number of results
+ * @param offset Number of results to skip
+ * @param responseFormat Output format
+ * @param config Configuration object
+ */
+export async function searchByPlatform(
+  query: string,
+  platform: string = 'youtube',
+  maxResults: number = 10,
+  offset: number = 0,
+  responseFormat: "json" | "markdown" = "markdown",
+  config: Config
+): Promise<string> {
+  // Currently only supports YouTube, can be expanded to other platforms in the future
+  if (platform.toLowerCase() !== 'youtube') {
+    throw new Error(`Currently only supports YouTube search, ${platform} is not supported`);
+  }
+
+  return searchVideos(query, maxResults, offset, responseFormat, config);
+} 

src/modules/subtitle.ts

@@ -0,0 +1,229 @@
+import * as fs from "fs";
+import * as path from "path";
+import * as os from "os";
+import type { Config } from '../config.js';
+import { getCookieArgs } from '../config.js';
+import { _spawnPromise, validateUrl, cleanSubtitleToTranscript } from "./utils.js";
+
+/**
+ * Lists all available subtitles for a video.
+ *
+ * @param url - The URL of the video
+ * @param config - Configuration object (optional, for cookie support)
+ * @returns Promise resolving to a string containing the list of available subtitles
+ * @throws {Error} When URL is invalid or subtitle listing fails
+ *
+ * @example
+ * ```typescript
+ * try {
+ *   const subtitles = await listSubtitles('https://youtube.com/watch?v=...', config);
+ *   console.log('Available subtitles:', subtitles);
+ * } catch (error) {
+ *   console.error('Failed to list subtitles:', error);
+ * }
+ * ```
+ */
+export async function listSubtitles(url: string, config?: Config): Promise<string> {
+  if (!validateUrl(url)) {
+    throw new Error('Invalid or unsupported URL format. Please provide a valid video URL (e.g., https://youtube.com/watch?v=...)');
+  }
+
+  try {
+    const args = [
+      '--ignore-config',
+      '--list-subs',
+      '--write-auto-sub',
+      '--skip-download',
+      '--verbose',
+      ...(config ? getCookieArgs(config) : []),
+      url
+    ];
+    const output = await _spawnPromise('yt-dlp', args);
+    return output;
+  } catch (error) {
+    if (error instanceof Error) {
+      if (error.message.includes("Unsupported URL") || error.message.includes("not supported")) {
+        throw new Error(`Unsupported platform or video URL: ${url}. Ensure the URL is from a supported platform like YouTube.`);
+      }
+      if (error.message.includes("Video unavailable") || error.message.includes("private")) {
+        throw new Error(`Video is unavailable or private: ${url}. Check the URL and video privacy settings.`);
+      }
+      if (error.message.includes("network") || error.message.includes("Connection")) {
+        throw new Error("Network error while fetching subtitles. Check your internet connection and retry.");
+      }
+    }
+    throw error;
+  }
+}
+
+/**
+ * Downloads subtitles for a video in the specified language.
+ * 
+ * @param url - The URL of the video
+ * @param language - Language code (e.g., 'en', 'zh-Hant', 'ja')
+ * @param config - Configuration object
+ * @returns Promise resolving to the subtitle content
+ * @throws {Error} When URL is invalid, language is not available, or download fails
+ * 
+ * @example
+ * ```typescript
+ * try {
+ *   // Download English subtitles
+ *   const enSubs = await downloadSubtitles('https://youtube.com/watch?v=...', 'en', config);
+ *   console.log('English subtitles:', enSubs);
+ * 
+ *   // Download Traditional Chinese subtitles
+ *   const zhSubs = await downloadSubtitles('https://youtube.com/watch?v=...', 'zh-Hant', config);
+ *   console.log('Chinese subtitles:', zhSubs);
+ * } catch (error) {
+ *   if (error.message.includes('No subtitle files found')) {
+ *     console.warn('No subtitles available in the requested language');
+ *   } else {
+ *     console.error('Failed to download subtitles:', error);
+ *   }
+ * }
+ * ```
+ */
+export async function downloadSubtitles(
+  url: string,
+  language: string,
+  config: Config
+): Promise<string> {
+  if (!validateUrl(url)) {
+    throw new Error('Invalid or unsupported URL format. Please provide a valid video URL (e.g., https://youtube.com/watch?v=...)');
+  }
+
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), config.file.tempDirPrefix));
+
+  try {
+    await _spawnPromise('yt-dlp', [
+      '--ignore-config',
+      '--write-sub',
+      '--write-auto-sub',
+      '--sub-lang', language,
+      '--skip-download',
+      '--output', path.join(tempDir, '%(title)s.%(ext)s'),
+      ...getCookieArgs(config),
+      url
+    ]);
+
+    const subtitleFiles = fs.readdirSync(tempDir)
+      .filter(file => file.endsWith('.vtt'));
+
+    if (subtitleFiles.length === 0) {
+      throw new Error(`No subtitle files found for language '${language}'. Use ytdlp_list_subtitle_languages to check available options.`);
+    }
+
+    let output = '';
+    for (const file of subtitleFiles) {
+      output += fs.readFileSync(path.join(tempDir, file), 'utf8');
+    }
+
+    // Check character limit
+    if (output.length > config.limits.characterLimit) {
+      output = output.substring(0, config.limits.characterLimit);
+      output += "\n\n⚠️ Subtitle content truncated due to size. Consider using ytdlp_download_transcript for plain text.";
+    }
+
+    return output;
+  } catch (error) {
+    if (error instanceof Error) {
+      if (error.message.includes("Unsupported URL") || error.message.includes("not supported")) {
+        throw new Error(`Unsupported platform or video URL: ${url}. Ensure the URL is from a supported platform like YouTube.`);
+      }
+      if (error.message.includes("Video unavailable") || error.message.includes("private")) {
+        throw new Error(`Video is unavailable or private: ${url}. Check the URL and video privacy settings.`);
+      }
+      if (error.message.includes("network") || error.message.includes("Connection")) {
+        throw new Error("Network error while downloading subtitles. Check your internet connection and retry.");
+      }
+    }
+    throw error;
+  } finally {
+    fs.rmSync(tempDir, { recursive: true, force: true });
+  }
+}
+
+/**
+ * Downloads and cleans subtitles to produce a plain text transcript.
+ * 
+ * @param url - The URL of the video
+ * @param language - Language code (e.g., 'en', 'zh-Hant', 'ja')
+ * @param config - Configuration object
+ * @returns Promise resolving to the cleaned transcript text
+ * @throws {Error} When URL is invalid, language is not available, or download fails
+ * 
+ * @example
+ * ```typescript
+ * try {
+ *   const transcript = await downloadTranscript('https://youtube.com/watch?v=...', 'en', config);
+ *   console.log('Transcript:', transcript);
+ * } catch (error) {
+ *   console.error('Failed to download transcript:', error);
+ * }
+ * ```
+ */
+export async function downloadTranscript(
+  url: string,
+  language: string,
+  config: Config
+): Promise<string> {
+  if (!validateUrl(url)) {
+    throw new Error('Invalid or unsupported URL format. Please provide a valid video URL (e.g., https://youtube.com/watch?v=...)');
+  }
+
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), config.file.tempDirPrefix));
+
+  try {
+    await _spawnPromise('yt-dlp', [
+      '--ignore-config',
+      '--skip-download',
+      '--write-subs',
+      '--write-auto-subs',
+      '--sub-lang', language,
+      '--sub-format', 'ttml',
+      '--convert-subs', 'srt',
+      '--output', path.join(tempDir, 'transcript.%(ext)s'),
+      ...getCookieArgs(config),
+      url
+    ]);
+
+    const srtFiles = fs.readdirSync(tempDir)
+      .filter(file => file.endsWith('.srt'));
+
+    if (srtFiles.length === 0) {
+      throw new Error(`No subtitle files found for transcript generation in language '${language}'. Use ytdlp_list_subtitle_languages to check available options.`);
+    }
+
+    let transcriptContent = '';
+    for (const file of srtFiles) {
+      const srtContent = fs.readFileSync(path.join(tempDir, file), 'utf8');
+      transcriptContent += cleanSubtitleToTranscript(srtContent) + ' ';
+    }
+
+    transcriptContent = transcriptContent.trim();
+
+    // Transcripts can be larger than standard limit
+    if (transcriptContent.length > config.limits.maxTranscriptLength) {
+      const truncated = transcriptContent.substring(0, config.limits.maxTranscriptLength);
+      transcriptContent = truncated + "\n\n⚠️ Transcript truncated due to length. This is a partial transcript.";
+    }
+
+    return transcriptContent;
+  } catch (error) {
+    if (error instanceof Error) {
+      if (error.message.includes("Unsupported URL") || error.message.includes("not supported")) {
+        throw new Error(`Unsupported platform or video URL: ${url}. Ensure the URL is from a supported platform like YouTube.`);
+      }
+      if (error.message.includes("Video unavailable") || error.message.includes("private")) {
+        throw new Error(`Video is unavailable or private: ${url}. Check the URL and video privacy settings.`);
+      }
+      if (error.message.includes("network") || error.message.includes("Connection")) {
+        throw new Error("Network error while downloading transcript. Check your internet connection and retry.");
+      }
+    }
+    throw error;
+  } finally {
+    fs.rmSync(tempDir, { recursive: true, force: true });
+  }
+} 

src/modules/utils.ts

@@ -0,0 +1,188 @@
+import * as fs from 'fs';
+import { spawn } from 'child_process';
+import { randomBytes } from 'crypto';
+
+/**
+ * Validates if a given string is a valid URL.
+ * 
+ * @param url - The URL string to validate
+ * @returns True if the URL is valid, false otherwise
+ * 
+ * @example
+ * ```typescript
+ * if (validateUrl('https://youtube.com/watch?v=...')) {
+ *   // URL is valid
+ * }
+ * ```
+ */
+export function validateUrl(url: string): boolean {
+  try {
+    new URL(url);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Checks if a URL is from YouTube.
+ * 
+ * @param url - The URL to check
+ * @returns True if the URL is from YouTube, false otherwise
+ * 
+ * @example
+ * ```typescript
+ * if (isYouTubeUrl('https://youtube.com/watch?v=...')) {
+ *   // URL is from YouTube
+ * }
+ * ```
+ */
+export function isYouTubeUrl(url: string): boolean {
+  try {
+    const parsedUrl = new URL(url);
+    return parsedUrl.hostname.includes('youtube.com') || parsedUrl.hostname.includes('youtu.be');
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Safely cleans up a directory and its contents.
+ * 
+ * @param directory - Path to the directory to clean up
+ * @returns Promise that resolves when cleanup is complete
+ * @throws {Error} When directory cannot be removed
+ * 
+ * @example
+ * ```typescript
+ * try {
+ *   await safeCleanup('/path/to/temp/dir');
+ * } catch (error) {
+ *   console.error('Cleanup failed:', error);
+ * }
+ * ```
+ */
+export async function safeCleanup(directory: string): Promise<void> {
+  try {
+    await fs.promises.rm(directory, { recursive: true, force: true });
+  } catch (error) {
+    console.error(`Error cleaning up directory ${directory}:`, error);
+  }
+}
+
+/**
+ * Spawns a child process and returns its output as a promise.
+ * 
+ * @param command - The command to execute
+ * @param args - Array of command arguments
+ * @returns Promise resolving to the command output
+ * @throws {Error} When command execution fails
+ * 
+ * @example
+ * ```typescript
+ * try {
+ *   const output = await _spawnPromise('yt-dlp', ['--version']);
+ *   console.log('yt-dlp version:', output);
+ * } catch (error) {
+ *   console.error('Command failed:', error);
+ * }
+ * ```
+ */
+export function _spawnPromise(command: string, args: string[]): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const process = spawn(command, args);
+    let stdout = '';
+    let stderr = '';
+
+    process.on('error', (err) => {
+      reject(new Error(`Failed to spawn ${command}: ${err.message}`));
+    });
+
+    process.stdout.on('data', (data) => {
+      stdout += data.toString();
+    });
+
+    process.stderr.on('data', (data) => {
+      stderr += data.toString();
+    });
+
+    process.on('close', (code) => {
+      if (code === 0) {
+        resolve(stdout);
+      } else {
+        reject(new Error(`Failed with exit code: ${code}\n${stderr}\n${stdout}`));
+      }
+    });
+  });
+}
+
+/**
+ * Generates a formatted timestamp string for file naming.
+ * 
+ * @returns Formatted timestamp string in the format 'YYYY-MM-DD_HH-mm-ss'
+ * 
+ * @example
+ * ```typescript
+ * const timestamp = getFormattedTimestamp();
+ * console.log(timestamp); // '2024-03-20_12-30-00'
+ * ```
+ */
+export function getFormattedTimestamp(): string {
+  return new Date().toISOString()
+    .replace(/[:.]/g, '-')
+    .replace('T', '_')
+    .split('.')[0];
+}
+
+/**
+ * Generates a random filename with timestamp prefix.
+ * 
+ * @param extension - Optional file extension (default: 'mp4')
+ * @returns A random filename with timestamp
+ * 
+ * @example
+ * ```typescript
+ * const filename = generateRandomFilename('mp3');
+ * console.log(filename); // '2024-03-20_12-30-00_a1b2c3d4.mp3'
+ * ```
+ */
+export function generateRandomFilename(extension: string = 'mp4'): string {
+  const timestamp = getFormattedTimestamp();
+  const randomId = randomBytes(4).toString('hex');
+  return `${timestamp}_${randomId}.${extension}`;
+}
+
+/**
+ * Cleans SRT subtitle content to produce a plain text transcript.
+ * Removes timestamps, sequence numbers, and HTML tags.
+ * 
+ * @param srtContent - Raw SRT subtitle content
+ * @returns Cleaned transcript text
+ * 
+ * @example
+ * ```typescript
+ * const cleanedText = cleanSubtitleToTranscript(srtContent);
+ * console.log(cleanedText); // 'Hello world this is a transcript...'
+ * ```
+ */
+export function cleanSubtitleToTranscript(srtContent: string): string {
+  return srtContent
+    .split('\n')
+    .filter(line => {
+      const trimmed = line.trim();
+      // Remove empty lines
+      if (!trimmed) return false;
+      // Remove sequence numbers (lines that are just digits)
+      if (/^\d+$/.test(trimmed)) return false;
+      // Remove timestamp lines
+      if (/^\d{2}:\d{2}:\d{2}[.,]\d{3}\s*-->\s*\d{2}:\d{2}:\d{2}[.,]\d{3}$/.test(trimmed)) return false;
+      return true;
+    })
+    .map(line => {
+      // Remove HTML tags
+      return line.replace(/<[^>]*>/g, '');
+    })
+    .join(' ')
+    .replace(/\s+/g, ' ')
+    .trim();
+} 

src/modules/video.ts

@@ -0,0 +1,176 @@
+import * as path from "path";
+import type { Config } from "../config.js";
+import { sanitizeFilename, getCookieArgs } from "../config.js";
+import {
+  _spawnPromise,
+  validateUrl,
+  getFormattedTimestamp,
+  isYouTubeUrl,
+  generateRandomFilename
+} from "./utils.js";
+
+/**
+ * Downloads a video from the specified URL.
+ *
+ * @param url - The URL of the video to download
+ * @param config - Configuration object for download settings
+ * @param resolution - Preferred video resolution ('480p', '720p', '1080p', 'best')
+ * @param startTime - Optional start time for trimming (format: HH:MM:SS[.ms])
+ * @param endTime - Optional end time for trimming (format: HH:MM:SS[.ms])
+ * @returns Promise resolving to a success message with the downloaded file path
+ * @throws {Error} When URL is invalid or download fails
+ *
+ * @example
+ * ```typescript
+ * // Download with default settings
+ * const result = await downloadVideo('https://youtube.com/watch?v=...');
+ * console.log(result);
+ *
+ * // Download with specific resolution
+ * const hdResult = await downloadVideo(
+ *   'https://youtube.com/watch?v=...',
+ *   undefined,
+ *   '1080p'
+ * );
+ * console.log(hdResult);
+ *
+ * // Download with trimming
+ * const trimmedResult = await downloadVideo(
+ *   'https://youtube.com/watch?v=...',
+ *   undefined,
+ *   '720p',
+ *   '00:01:30',
+ *   '00:02:45'
+ * );
+ * console.log(trimmedResult);
+ * ```
+ */
+export async function downloadVideo(
+  url: string,
+  config: Config,
+  resolution: "480p" | "720p" | "1080p" | "best" = "720p",
+  startTime?: string,
+  endTime?: string
+): Promise<string> {
+  const userDownloadsDir = config.file.downloadsDir;
+
+  if (!validateUrl(url)) {
+    throw new Error("Invalid or unsupported URL format");
+  }
+
+  try {
+    const timestamp = getFormattedTimestamp();
+
+    let format: string;
+    if (isYouTubeUrl(url)) {
+      // YouTube-specific format selection
+      switch (resolution) {
+        case "480p":
+          format = "bestvideo[height<=480]+bestaudio/best[height<=480]/best";
+          break;
+        case "720p":
+          format = "bestvideo[height<=720]+bestaudio/best[height<=720]/best";
+          break;
+        case "1080p":
+          format = "bestvideo[height<=1080]+bestaudio/best[height<=1080]/best";
+          break;
+        case "best":
+          format = "bestvideo+bestaudio/best";
+          break;
+        default:
+          format = "bestvideo[height<=720]+bestaudio/best[height<=720]/best";
+      }
+    } else {
+      // For other platforms, use quality labels that are more generic
+      switch (resolution) {
+        case "480p":
+          format = "worst[height>=480]/best[height<=480]/worst";
+          break;
+        case "best":
+          format = "bestvideo+bestaudio/best";
+          break;
+        default: // Including 720p and 1080p cases
+          // Prefer HD quality but fallback to best available
+          format = "bestvideo[height>=720]+bestaudio/best[height>=720]/best";
+      }
+    }
+
+    let outputTemplate: string;
+    let expectedFilename: string;
+
+    try {
+      // 嘗試獲取檔案名稱
+      outputTemplate = path.join(
+        userDownloadsDir,
+        sanitizeFilename(`%(title)s [%(id)s] ${timestamp}`, config.file) + '.%(ext)s'
+      );
+
+      const getFilenameArgs = [
+        "--ignore-config",
+        "--get-filename",
+        "-f", format,
+        "--output", outputTemplate,
+        ...getCookieArgs(config),
+        url
+      ];
+      expectedFilename = await _spawnPromise("yt-dlp", getFilenameArgs);
+      expectedFilename = expectedFilename.trim();
+    } catch (error) {
+      // 如果無法獲取檔案名稱，使用隨機檔案名
+      const randomFilename = generateRandomFilename('mp4');
+      outputTemplate = path.join(userDownloadsDir, randomFilename);
+      expectedFilename = randomFilename;
+    }
+
+    // Build download arguments
+    const downloadArgs = [
+      "--ignore-config",
+      "--progress",
+      "--newline",
+      "--no-mtime",
+      "-f", format,
+      "--output", outputTemplate,
+      ...getCookieArgs(config)
+    ];
+
+    // Add trimming parameters if provided
+    if (startTime || endTime) {
+      let downloadSection = "*";
+      
+      if (startTime && endTime) {
+        downloadSection = `*${startTime}-${endTime}`;
+      } else if (startTime) {
+        downloadSection = `*${startTime}-`;
+      } else if (endTime) {
+        downloadSection = `*-${endTime}`;
+      }
+
+      downloadArgs.push("--download-sections", downloadSection, "--force-keyframes-at-cuts");
+    }
+
+    downloadArgs.push(url);
+
+    // Download with progress info
+    try {
+      await _spawnPromise("yt-dlp", downloadArgs);
+    } catch (error) {
+      if (error instanceof Error) {
+        if (error.message.includes("Unsupported URL") || error.message.includes("extractor")) {
+          throw new Error(`Unsupported platform or video URL: ${url}. Ensure the URL is from a supported platform.`);
+        }
+        if (error.message.includes("Video unavailable") || error.message.includes("private")) {
+          throw new Error(`Video is unavailable or private: ${url}. Check the URL and video privacy settings.`);
+        }
+        if (error.message.includes("network") || error.message.includes("Connection")) {
+          throw new Error("Network error during download. Check your internet connection and retry.");
+        }
+        throw new Error(`Download failed: ${error.message}. Check URL and try again.`);
+      }
+      throw new Error(`Download failed: ${String(error)}`);
+    }
+
+    return `Video successfully downloaded as "${path.basename(expectedFilename)}" to ${userDownloadsDir}`;
+  } catch (error) {
+    throw error;
+  }
+} 

tests/test-bilibili.mjs

@@ -0,0 +1,224 @@
+#!/usr/bin/env node
+/**
+ * Test MCP server with Bilibili video
+ * Tests cross-platform support with https://www.bilibili.com/video/BV17YdXY4Ewj/
+ */
+
+import { spawn } from 'child_process';
+import { fileURLToPath } from 'url';
+import { dirname, join } from 'path';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+const serverPath = join(__dirname, 'lib', 'index.mjs');
+const TEST_VIDEO = 'https://www.bilibili.com/video/BV17YdXY4Ewj/?spm_id_from=333.1387.homepage.video_card.click&vd_source=bc7bf10259efd682c452b5ce8426b945';
+
+console.log('🎬 Testing yt-dlp MCP Server with Bilibili Video\n');
+console.log('Video:', TEST_VIDEO);
+console.log('Platform: Bilibili (哔哩哔哩)\n');
+
+const server = spawn('node', [serverPath]);
+
+let testsPassed = 0;
+let testsFailed = 0;
+let responseBuffer = '';
+let requestId = 0;
+let currentTest = '';
+
+const timeout = setTimeout(() => {
+  console.log('\n⏱️  Test timeout - killing server');
+  server.kill();
+  printResults();
+}, 60000);
+
+function printResults() {
+  clearTimeout(timeout);
+  console.log(`\n${'='.repeat(60)}`);
+  console.log(`📊 Bilibili Test Results:`);
+  console.log(`   ✅ Passed: ${testsPassed}`);
+  console.log(`   ❌ Failed: ${testsFailed}`);
+  console.log(`${'='.repeat(60)}`);
+
+  if (testsPassed > 0) {
+    console.log('\n✨ Bilibili platform is supported!');
+  } else {
+    console.log('\n⚠️  Bilibili support may be limited');
+  }
+
+  process.exit(testsFailed > 0 ? 1 : 0);
+}
+
+server.stdout.on('data', (data) => {
+  responseBuffer += data.toString();
+
+  const lines = responseBuffer.split('\n');
+  responseBuffer = lines.pop() || '';
+
+  lines.forEach(line => {
+    if (line.trim()) {
+      try {
+        const response = JSON.parse(line);
+
+        if (response.error) {
+          console.log(`❌ ${currentTest} - ERROR`);
+          console.log('   Error:', response.error.message);
+          console.log('   This may indicate limited Bilibili support\n');
+          testsFailed++;
+        } else if (response.result) {
+          handleTestResult(response);
+        }
+      } catch (e) {
+        // Not JSON
+      }
+    }
+  });
+});
+
+server.stderr.on('data', (data) => {
+  const output = data.toString().trim();
+  if (output && !output.includes('ExperimentalWarning')) {
+    console.log('🔧 Server:', output);
+  }
+});
+
+server.on('close', (code) => {
+  printResults();
+});
+
+function handleTestResult(response) {
+  const content = response.result.content?.[0]?.text || JSON.stringify(response.result);
+
+  if (currentTest === 'Initialize') {
+    console.log('✅ Initialize - PASSED\n');
+    testsPassed++;
+  }
+  else if (currentTest === 'Get Bilibili Metadata Summary') {
+    // Check if we got any content
+    if (content && content.length > 50 && !content.includes('Error')) {
+      console.log('✅ Get Bilibili Metadata Summary - PASSED');
+      console.log('   Response preview:');
+      const lines = content.split('\n').slice(0, 8);
+      lines.forEach(line => console.log(`   ${line}`));
+      if (content.split('\n').length > 8) {
+        console.log('   ...');
+      }
+      console.log();
+      testsPassed++;
+    } else if (content.includes('Error') || content.includes('Unsupported')) {
+      console.log('⚠️  Get Bilibili Metadata Summary - PARTIAL');
+      console.log('   Platform may have limited support');
+      console.log('   Response:', content.substring(0, 150));
+      console.log();
+      testsFailed++;
+    } else {
+      console.log('❌ Get Bilibili Metadata Summary - FAILED');
+      console.log('   Response too short or invalid');
+      console.log();
+      testsFailed++;
+    }
+  }
+  else if (currentTest === 'List Bilibili Subtitle Languages') {
+    if (content.length > 50 && !content.includes('Error')) {
+      console.log('✅ List Bilibili Subtitle Languages - PASSED');
+      console.log('   Subtitle info retrieved\n');
+      testsPassed++;
+    } else if (content.includes('No subtitle') || content.includes('not found')) {
+      console.log('⚠️  List Bilibili Subtitle Languages - NO SUBTITLES');
+      console.log('   Video may not have subtitles available\n');
+      testsPassed++; // Not an error, just no subs
+    } else {
+      console.log('❌ List Bilibili Subtitle Languages - FAILED');
+      console.log('   Response:', content.substring(0, 200));
+      console.log();
+      testsFailed++;
+    }
+  }
+  else if (currentTest === 'Get Bilibili Metadata (Filtered)') {
+    try {
+      const metadata = JSON.parse(content);
+      if (metadata.id || metadata.title) {
+        console.log('✅ Get Bilibili Metadata (Filtered) - PASSED');
+        if (metadata.title) console.log(`   Title: ${metadata.title}`);
+        if (metadata.uploader) console.log(`   Uploader: ${metadata.uploader}`);
+        if (metadata.duration) console.log(`   Duration: ${metadata.duration}s`);
+        console.log();
+        testsPassed++;
+      } else {
+        console.log('❌ Get Bilibili Metadata (Filtered) - FAILED');
+        console.log('   Missing expected fields');
+        console.log();
+        testsFailed++;
+      }
+    } catch (e) {
+      // Maybe it's an error message
+      if (content.includes('Error') || content.includes('Unsupported')) {
+        console.log('⚠️  Get Bilibili Metadata (Filtered) - PLATFORM ISSUE');
+        console.log('   Response:', content.substring(0, 200));
+        console.log();
+        testsFailed++;
+      } else {
+        console.log('❌ Get Bilibili Metadata (Filtered) - FAILED');
+        console.log('   Invalid response format');
+        console.log();
+        testsFailed++;
+      }
+    }
+  }
+}
+
+function sendRequest(method, params, testName) {
+  requestId++;
+  currentTest = testName;
+  console.log(`🔍 Test ${requestId}: ${testName}`);
+  if (testName.includes('Metadata') || testName.includes('Subtitle')) {
+    console.log('   (Testing Bilibili platform support...)\n');
+  }
+
+  const request = {
+    jsonrpc: '2.0',
+    id: requestId,
+    method: method,
+    params: params
+  };
+
+  server.stdin.write(JSON.stringify(request) + '\n');
+}
+
+// Run tests
+setTimeout(() => {
+  sendRequest('initialize', {
+    protocolVersion: '2024-11-05',
+    capabilities: {},
+    clientInfo: { name: 'bilibili-test', version: '1.0.0' }
+  }, 'Initialize');
+
+  setTimeout(() => {
+    sendRequest('tools/call', {
+      name: 'ytdlp_get_video_metadata_summary',
+      arguments: { url: TEST_VIDEO }
+    }, 'Get Bilibili Metadata Summary');
+
+    setTimeout(() => {
+      sendRequest('tools/call', {
+        name: 'ytdlp_list_subtitle_languages',
+        arguments: { url: TEST_VIDEO }
+      }, 'List Bilibili Subtitle Languages');
+
+      setTimeout(() => {
+        sendRequest('tools/call', {
+          name: 'ytdlp_get_video_metadata',
+          arguments: {
+            url: TEST_VIDEO,
+            fields: ['id', 'title', 'uploader', 'duration', 'description']
+          }
+        }, 'Get Bilibili Metadata (Filtered)');
+
+        setTimeout(() => {
+          console.log('\n✅ All Bilibili tests completed!');
+          server.kill();
+        }, 8000);
+      }, 5000);
+    }, 5000);
+  }, 2000);
+}, 1000);

tests/test-mcp.mjs

@@ -0,0 +1,105 @@
+#!/usr/bin/env node
+/**
+ * Simple MCP protocol test
+ * This script tests if the MCP server responds correctly to basic protocol messages
+ */
+
+import { spawn } from 'child_process';
+import { fileURLToPath } from 'url';
+import { dirname, join } from 'path';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+const serverPath = join(__dirname, 'lib', 'index.mjs');
+
+console.log('🧪 Testing yt-dlp MCP Server\n');
+console.log('Starting server from:', serverPath);
+
+const server = spawn('node', [serverPath]);
+
+let testsPassed = 0;
+let testsFailed = 0;
+let responseBuffer = '';
+
+// Timeout to ensure tests complete
+const timeout = setTimeout(() => {
+  console.log('\n⏱️  Test timeout - killing server');
+  server.kill();
+  process.exit(testsFailed > 0 ? 1 : 0);
+}, 10000);
+
+server.stdout.on('data', (data) => {
+  responseBuffer += data.toString();
+
+  // Try to parse JSON-RPC responses
+  const lines = responseBuffer.split('\n');
+  responseBuffer = lines.pop() || ''; // Keep incomplete line in buffer
+
+  lines.forEach(line => {
+    if (line.trim()) {
+      try {
+        const response = JSON.parse(line);
+        console.log('📨 Received:', JSON.stringify(response, null, 2));
+
+        if (response.result) {
+          testsPassed++;
+          console.log('✅ Test passed\n');
+        }
+      } catch (e) {
+        // Not JSON, might be regular output
+        console.log('📝 Output:', line);
+      }
+    }
+  });
+});
+
+server.stderr.on('data', (data) => {
+  console.log('🔧 Server log:', data.toString().trim());
+});
+
+server.on('close', (code) => {
+  clearTimeout(timeout);
+  console.log(`\n📊 Test Results:`);
+  console.log(`   ✅ Passed: ${testsPassed}`);
+  console.log(`   ❌ Failed: ${testsFailed}`);
+  console.log(`   Server exit code: ${code}`);
+  process.exit(testsFailed > 0 ? 1 : 0);
+});
+
+// Wait a bit for server to start
+setTimeout(() => {
+  console.log('\n🔍 Test 1: Initialize');
+  const initRequest = {
+    jsonrpc: '2.0',
+    id: 1,
+    method: 'initialize',
+    params: {
+      protocolVersion: '2024-11-05',
+      capabilities: {},
+      clientInfo: {
+        name: 'test-client',
+        version: '1.0.0'
+      }
+    }
+  };
+
+  server.stdin.write(JSON.stringify(initRequest) + '\n');
+
+  setTimeout(() => {
+    console.log('\n🔍 Test 2: List Tools');
+    const listToolsRequest = {
+      jsonrpc: '2.0',
+      id: 2,
+      method: 'tools/list',
+      params: {}
+    };
+
+    server.stdin.write(JSON.stringify(listToolsRequest) + '\n');
+
+    setTimeout(() => {
+      console.log('\n✅ Basic protocol tests completed');
+      server.kill();
+    }, 2000);
+  }, 2000);
+}, 1000);

tests/test-real-video.mjs

@@ -0,0 +1,215 @@
+#!/usr/bin/env node
+/**
+ * Real-world MCP server test with actual YouTube video
+ * Tests multiple tools with https://www.youtube.com/watch?v=dQw4w9WgXcQ
+ */
+
+import { spawn } from 'child_process';
+import { fileURLToPath } from 'url';
+import { dirname, join } from 'path';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+const serverPath = join(__dirname, 'lib', 'index.mjs');
+const TEST_VIDEO = 'https://www.youtube.com/watch?v=dQw4w9WgXcQ';
+
+console.log('🎬 Testing yt-dlp MCP Server with Real Video\n');
+console.log('Video:', TEST_VIDEO);
+console.log('Starting server from:', serverPath, '\n');
+
+const server = spawn('node', [serverPath]);
+
+let testsPassed = 0;
+let testsFailed = 0;
+let responseBuffer = '';
+let requestId = 0;
+let currentTest = '';
+
+// Timeout to ensure tests complete
+const timeout = setTimeout(() => {
+  console.log('\n⏱️  Test timeout - killing server');
+  server.kill();
+  printResults();
+}, 60000); // 60 seconds for real API calls
+
+function printResults() {
+  clearTimeout(timeout);
+  console.log(`\n${'='.repeat(60)}`);
+  console.log(`📊 Final Test Results:`);
+  console.log(`   ✅ Passed: ${testsPassed}`);
+  console.log(`   ❌ Failed: ${testsFailed}`);
+  console.log(`${'='.repeat(60)}`);
+  process.exit(testsFailed > 0 ? 1 : 0);
+}
+
+server.stdout.on('data', (data) => {
+  responseBuffer += data.toString();
+
+  // Try to parse JSON-RPC responses
+  const lines = responseBuffer.split('\n');
+  responseBuffer = lines.pop() || '';
+
+  lines.forEach(line => {
+    if (line.trim()) {
+      try {
+        const response = JSON.parse(line);
+
+        if (response.error) {
+          console.log(`❌ ${currentTest} - ERROR`);
+          console.log('   Error:', response.error.message);
+          testsFailed++;
+        } else if (response.result) {
+          handleTestResult(response);
+        }
+      } catch (e) {
+        // Not JSON, might be regular output
+      }
+    }
+  });
+});
+
+server.stderr.on('data', (data) => {
+  const output = data.toString().trim();
+  if (output && !output.includes('ExperimentalWarning')) {
+    console.log('🔧 Server:', output);
+  }
+});
+
+server.on('close', (code) => {
+  printResults();
+});
+
+function handleTestResult(response) {
+  const content = response.result.content?.[0]?.text || JSON.stringify(response.result);
+
+  if (currentTest === 'Initialize') {
+    console.log('✅ Initialize - PASSED');
+    console.log(`   Protocol: ${response.result.protocolVersion}`);
+    console.log(`   Server: ${response.result.serverInfo.name} v${response.result.serverInfo.version}\n`);
+    testsPassed++;
+  }
+  else if (currentTest === 'Get Metadata Summary') {
+    if (content.includes('Rick Astley') || content.includes('Never Gonna Give You Up')) {
+      console.log('✅ Get Metadata Summary - PASSED');
+      console.log('   Response preview:');
+      const lines = content.split('\n').slice(0, 5);
+      lines.forEach(line => console.log(`   ${line}`));
+      console.log('   ...\n');
+      testsPassed++;
+    } else {
+      console.log('❌ Get Metadata Summary - FAILED');
+      console.log('   Expected Rick Astley content, got:', content.substring(0, 100));
+      testsFailed++;
+    }
+  }
+  else if (currentTest === 'List Subtitle Languages') {
+    if (content.includes('en') || content.includes('English')) {
+      console.log('✅ List Subtitle Languages - PASSED');
+      console.log('   Found subtitle languages\n');
+      testsPassed++;
+    } else {
+      console.log('❌ List Subtitle Languages - FAILED');
+      console.log('   Response:', content.substring(0, 200));
+      testsFailed++;
+    }
+  }
+  else if (currentTest === 'Get Metadata (Filtered)') {
+    try {
+      const metadata = JSON.parse(content);
+      if (metadata.title && metadata.channel) {
+        console.log('✅ Get Metadata (Filtered) - PASSED');
+        console.log(`   Title: ${metadata.title}`);
+        console.log(`   Channel: ${metadata.channel}`);
+        console.log(`   Duration: ${metadata.duration || 'N/A'}\n`);
+        testsPassed++;
+      } else {
+        console.log('❌ Get Metadata (Filtered) - FAILED');
+        console.log('   Missing expected fields');
+        testsFailed++;
+      }
+    } catch (e) {
+      console.log('❌ Get Metadata (Filtered) - FAILED');
+      console.log('   Invalid JSON response');
+      testsFailed++;
+    }
+  }
+  else if (currentTest === 'Download Transcript (first 500 chars)') {
+    if (content.length > 100) {
+      console.log('✅ Download Transcript - PASSED');
+      console.log('   Transcript length:', content.length, 'characters');
+      console.log('   Preview:', content.substring(0, 150).replace(/\n/g, ' ') + '...\n');
+      testsPassed++;
+    } else {
+      console.log('❌ Download Transcript - FAILED');
+      console.log('   Response too short:', content.substring(0, 100));
+      testsFailed++;
+    }
+  }
+}
+
+function sendRequest(method, params, testName) {
+  requestId++;
+  currentTest = testName;
+  console.log(`🔍 Test ${requestId}: ${testName}`);
+
+  const request = {
+    jsonrpc: '2.0',
+    id: requestId,
+    method: method,
+    params: params
+  };
+
+  server.stdin.write(JSON.stringify(request) + '\n');
+}
+
+// Run tests sequentially with delays
+setTimeout(() => {
+  // Test 1: Initialize
+  sendRequest('initialize', {
+    protocolVersion: '2024-11-05',
+    capabilities: {},
+    clientInfo: { name: 'test-client', version: '1.0.0' }
+  }, 'Initialize');
+
+  setTimeout(() => {
+    // Test 2: Get video metadata summary
+    sendRequest('tools/call', {
+      name: 'ytdlp_get_video_metadata_summary',
+      arguments: { url: TEST_VIDEO }
+    }, 'Get Metadata Summary');
+
+    setTimeout(() => {
+      // Test 3: List subtitle languages
+      sendRequest('tools/call', {
+        name: 'ytdlp_list_subtitle_languages',
+        arguments: { url: TEST_VIDEO }
+      }, 'List Subtitle Languages');
+
+      setTimeout(() => {
+        // Test 4: Get specific metadata fields
+        sendRequest('tools/call', {
+          name: 'ytdlp_get_video_metadata',
+          arguments: {
+            url: TEST_VIDEO,
+            fields: ['id', 'title', 'channel', 'duration', 'view_count']
+          }
+        }, 'Get Metadata (Filtered)');
+
+        setTimeout(() => {
+          // Test 5: Download transcript (might take longer)
+          console.log('   (This may take 10-20 seconds...)\n');
+          sendRequest('tools/call', {
+            name: 'ytdlp_download_transcript',
+            arguments: { url: TEST_VIDEO, language: 'en' }
+          }, 'Download Transcript (first 500 chars)');
+
+          setTimeout(() => {
+            console.log('\n✅ All tests completed!');
+            server.kill();
+          }, 25000); // Wait 25 seconds for transcript
+        }, 3000);
+      }, 5000);
+    }, 5000);
+  }, 2000);
+}, 1000);