OpenAPI to MCP Generator (openapi-mcp-generator)

A command-line tool that generates a complete, buildable Model Context Protocol (MCP) server project in TypeScript from an OpenAPI specification. This tool helps you quickly create an MCP server using stdio transport that acts as a bridge between LLMs (Large Language Models) and your API.

Features

• Automatic Tool Generation: Converts each API operation in your OpenAPI spec into an MCP tool within the generated server.
• Complete Project Setup: Generates a full Node.js project structure (package.json, tsconfig.json, src/index.ts, .gitignore).
• TypeScript & Build Ready: Creates a TypeScript project configured for building into JavaScript for execution.
• Stdio Transport: Generated server uses standard input/output for communication with the MCP client (e.g., an LLM).
• Runtime Argument Validation: Integrates Zod for validating tool arguments at runtime based on the OpenAPI schema.

Installation

# Install globally from npm
npm install -g openapi-mcp-generator

# Or with yarn
yarn global add openapi-mcp-generator

# Or with pnpm
pnpm add -g openapi-mcp-generator

Usage

Generate an MCP server project from an OpenAPI specification:

openapi-mcp-generator -i <path_or_url_to_openapi> -o <output_directory_path> [options]

Command Line Options

Option	Alias	Description	Default
--input	-i	Path or URL to the OpenAPI specification file (JSON or YAML).	(Required)
--output	-o	Path to the directory where the MCP server project will be created.	(Required)
--name	-n	Name for the generated MCP server package (package.json).	Derived from OpenAPI title or my-mcp-server
--version	-v	Version for the generated MCP server package (package.json).	Derived from OpenAPI version or 0.1.0
--base-url	-b	Base URL for the target API. Required if not in OpenAPI servers or if multiple servers specified.	Derived from OpenAPI servers if possible
--help	-h	Show help information.

Examples

Generate from a local OpenAPI file:

openapi-mcp-generator -i ./specs/my-api.yaml -o ./my-api-mcp-server

Generate from a remote OpenAPI URL, specifying name and base URL:

openapi-mcp-generator \
  -i https://petstore3.swagger.io/api/v3/openapi.json \
  -o ./petstore-mcp \
  -n petstore-server \
  -b https://petstore3.swagger.io/api/v3

Generated Project Structure

The tool generates the following structure in the specified output directory:

<output_directory>/
├── .gitignore          # Standard Node.js gitignore
├── package.json        # Dependencies and scripts for the generated server
├── tsconfig.json       # TypeScript configuration for building
└── src/
    └── index.ts        # The generated MCP server source code

Using the Generated Server

After generating your MCP server project:

1. Navigate to the generated directory:

   cd <output_directory>
   # e.g., cd ./petstore-mcp
   

2. Install dependencies:

   npm install
   

   This installs @modelcontextprotocol/sdk, axios, zod, json-schema-to-zod, and typescript.

3. (Optional) Implement Authentication/Configuration:

   • The generator sets the API_BASE_URL constant in src/index.ts if provided or derived.
   • You will need to manually edit src/index.ts to add any necessary API authentication (e.g., setting Authorization headers in the AxiosRequestConfig using environment variables or other secure methods). Look for the // Add Authentication logic here if needed comment within the CallTool handler.

4. Build the server code:

   npm run build
   

   This compiles the TypeScript code from src/ into JavaScript in the build/ directory.

5. Start the server:

   npm start
   

   This runs the compiled JavaScript server (node build/index.js), which will listen for MCP requests on standard input/output.

Requirements

• Node.js v18.0.0 or higher (for both the generator and the generated server)

Contributing

Contributions are welcome! Please feel free to submit a Pull Request to the GitHub repository.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

License

MIT