OpenAPI to MCP Generator (openapi-mcp-generator)

Generate Model Context Protocol (MCP) servers from OpenAPI specifications.

This CLI tool automates the generation of MCP-compatible servers that proxy requests to existing REST APIs—enabling AI agents and other MCP clients to seamlessly interact with your APIs using either standard input/output or HTTP-based transport.

✨ Features

• 🔧 OpenAPI 3.0 Support: Converts any OpenAPI 3.0+ spec into an MCP-compatible server.
• 🔁 Proxy Behavior: Proxies calls to your original REST API while validating request structure and security.
• 🔐 Authentication Support: API keys, Bearer tokens, Basic auth, and OAuth2 supported via environment variables.
• 🧪 Zod Validation: Automatically generates Zod schemas from OpenAPI definitions for runtime input validation.
• ⚙️ Typed Server: Fully typed, maintainable TypeScript code output.
• 💬 Stdio & Web Transport: Communicate over stdio or HTTP (beta, SSE support).
• 🧰 Project Scaffold: Generates a complete Node.js project with tsconfig.json, package.json, and entry point.
• 🧪 Built-in HTML Test Client (Web mode): Test API interactions visually in your browser.

🚀 Installation

npm install -g openapi-mcp-generator

You can also use yarn global add openapi-mcp-generator or pnpm add -g openapi-mcp-generator

🛠 Usage

# Generate an MCP server (stdio)
openapi-mcp-generator --input path/to/openapi.json --output path/to/output/dir

# Generate an MCP web server (beta)
openapi-mcp-generator --input path/to/openapi.json --output path/to/output/dir --transport=web --port=3000

CLI Options

🧱 Project Structure

The generated project includes:

<output_directory>/
├── .gitignore
├── package.json
├── tsconfig.json
└── src/
    └── index.ts

• Uses axios, zod, @modelcontextprotocol/sdk, and json-schema-to-zod
• Secure API key/tokens via environment variables
• Tool generation for each endpoint

📡 Transport Modes

Stdio (Default)

Communicates with MCP clients via standard input/output. Ideal for local development or integration with LLM tools.

Web Server Mode (Beta)

Launches a fully functional HTTP server with:

• Server-Sent Events (SSE) for bidirectional messaging
• REST endpoint for client → server communication
• In-browser test client UI
• Multi-connection support

⚠️ Note: Web mode is experimental and may have breaking changes in future updates.

🔐 Environment Variables for Authentication

Configure auth credentials in your environment:

▶️ Running the Generated Server

cd path/to/output/dir
npm install

# Run in stdio mode
npm start

# Run in web server mode (if generated with --transport=web)
npm run start:web

⚠️ Requirements

• Node.js v18 or later

🤝 Contributing

Contributions are welcome!

1. Fork the repo
2. Create a feature branch: git checkout -b feature/amazing-feature
3. Commit your changes: git commit -m "Add amazing feature"
4. Push and open a PR

📌 Repository: github.com/harsha-iiiv/openapi-mcp-generator

📄 License

MIT License — see LICENSE for full details.