📌Overview

Purpose: To generate Model Context Protocol (MCP) server code from OpenAPI specifications, facilitating seamless integration between Large Language Models and APIs.

Overview: The OpenAPI to MCP Generator is a command-line tool designed to automate the creation of MCP server code. By converting OpenAPI specifications into fully functional MCP servers, it streamlines the development process and enhances the interoperability of APIs with LLMs.

Key Features:

• Automatic Tool Generation: Effortlessly translates each API endpoint from an OpenAPI specification into corresponding MCP tools, minimizing manual coding efforts.

• Multiple Transport Options: Offers flexibility in communication methods, supporting stdio, WebSocket, and HTTP, which allows for a wide range of application scenarios.

• Complete Project Setup: Automatically generates all essential files needed to run an MCP server, providing a ready-to-deploy environment.

• TypeScript Support: Includes TypeScript definitions, ensuring type safety and developer familiarity.

• Easy Configuration: Simplifies server setup through environment-based configuration, making it user-friendly for developers.

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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.

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✨ 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.

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🚀 Installation

npm install -g openapi-mcp-generator

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

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🛠 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

Option	Alias	Description	Default
--input	-i	Path or URL to OpenAPI specification (YAML or JSON)	Required
--output	-o	Directory to output the generated MCP project	Required
--server-name	-n	Name of the MCP server (package.json:name)	OpenAPI title or mcp-api-server
--server-version	-v	Version of the MCP server (package.json:version)	OpenAPI version or 1.0.0
--base-url	-b	Base URL for API requests. Required if OpenAPI servers missing or ambiguous.	Auto-detected if possible
--transport	-t	Transport mode: "stdio" (default) or "web" (beta)	"stdio"
--port	-p	Port for web server mode	3000
--force		Overwrite existing files in the output directory without confirmation	false

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🧱 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.

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📡 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.

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🔐 Environment Variables for Authentication

Configure auth credentials in your environment:

Auth Type	Variable Format
API Key	API_KEY_<SCHEME_NAME>
Bearer	BEARER_TOKEN_<SCHEME_NAME>
Basic Auth	BASIC_USERNAME_<SCHEME_NAME>, BASIC_PASSWORD_<SCHEME_NAME>
OAuth2	OAUTH_CLIENT_ID_<SCHEME_NAME>, OAUTH_CLIENT_SECRET_<SCHEME_NAME>, OAUTH_SCOPES_<SCHEME_NAME>

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▶️ 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

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⚠️ Requirements

• Node.js v18 or later

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🤝 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

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📄 License

MIT License — see LICENSE for full details.