yt-dlp-mcp/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Development Commands

Build and Prepare

npm run prepare  # Compile TypeScript and make binary executable

Testing

npm test  # Run Jest tests with ESM support

Manual Testing

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