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FastAPI MCP OpenAPI

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A FastAPI library that provides Model Context Protocol (MCP) tools for endpoint introspection and OpenAPI documentation. This library allows AI agents to discover and understand your FastAPI endpoints through MCP.

FastAPI MCP OpenAPI

Instantly turn your FastAPI app into an AI-friendly, fully introspectable MCP server for LLMs and agents like Cursor and GitHub Copilot in VS Code. Discover, document, and stream your endpoints for next-gen AI workflows.

Why use this?

  • Zero-effort LLM/MCP integration: Expose your FastAPI endpoints to AI agents, Cursor, GitHub Copilot, and other dev tools with a single line of code.
  • Seamless API doc connectivity: Tools like Cursor and Copilot can instantly discover and use your API docs for autocompletion, endpoint introspection, and more for app development.
  • Full OpenAPI support: Get detailed, resolved OpenAPI docs for every endpoint—no more guessing what your API does.
  • Streamable, modern protocol: Implements the latest MCP Streamable HTTP transport for real-time, agent-friendly workflows.
  • Security by default: CORS, origin validation, and session management out of the box.
  • Production-ready: Used in real-world AI agent stacks and developer tools.

Who's using this?

A FastAPI library that provides Model Context Protocol (MCP) tools for endpoint introspection and OpenAPI documentation. This library allows AI agents to discover and understand your FastAPI endpoints through MCP.

Features

  • Endpoint Discovery: Lists all available FastAPI endpoints with metadata
  • OpenAPI Documentation: Provides detailed OpenAPI schema for specific endpoints with fully resolved inline schemas
  • Clean Output: Removes unnecessary references and fields for minimal context usage
  • MCP Streamable HTTP Transport: Full compatibility with the latest MCP protocol (2025-03-26)
  • Easy Integration: Simple mounting system similar to fastapi-mcp
  • Security: Built-in CORS protection and origin validation
  • Focused Tool Set: Only provides tools capability - resources and prompts endpoints are disabled

🚀 Try it in 5 minutes

pip install fastapi-mcp-openapi
# or
uv add fastapi-mcp-openapi

Create a file called main.py:

from fastapi import FastAPI
from fastapi_mcp_openapi import FastAPIMCPOpenAPI

app = FastAPI(title="My API", version="1.0.0")

@app.get("/hello")
async def hello():
    return {"message": "Hello, world!"}

mcp = FastAPIMCPOpenAPI(app)

if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8000)

Run it:

python main.py

Visit http://localhost:8000/mcp to see your MCP server in action!

Your MCP server will be available at http://localhost:8000/mcp and provides two tools:

  1. listEndpoints: Get all available endpoints (excluding MCP endpoints)
  2. getEndpointDocs: Get detailed OpenAPI documentation for a specific endpoint

[!CAUTION]All API endpoints must be fully typed with Pydantic models or FastAPI's native types to ensure proper OpenAPI generation and MCP compatibility.

Configuration

Constructor Parameters

  • app: The FastAPI application to introspect
  • mount_path: Path where MCP server will be mounted (default: "/mcp")
  • server_name: Name of the MCP server (default: "fastapi-openapi-mcp")
  • server_version: Version of the MCP server (default: "0.1.0")
  • section_name: Name of the section in documentation for MCP endpoints (default: "mcp")
  • list_endpoints_tool_name: Name of the list endpoints tool (default: "listEndpoints")
  • get_endpoint_docs_tool_name: Name of the get endpoint docs tool (default: "getEndpointDocs")

Example with Custom Configuration

from fastapi import FastAPI
from fastapi_mcp_openapi import FastAPIMCPOpenAPI

app = FastAPI()

# Custom configuration
mcp = FastAPIMCPOpenAPI(
    app=app,
    mount_path="/api-mcp",
    server_name="Custom API Inspector",
    server_version="2.0.0"
    section_name="api-mcp",
    list_endpoints_tool_name="listApiEndpoints",
    get_endpoint_docs_tool_name="getApiEndpointDocs"
)

MCP Tools

1. listEndpoints

Lists all available FastAPI endpoints with their metadata.

Input: No parameters required

Output: JSON array of endpoint information including:

  • path: The endpoint path
  • methods: Array of HTTP methods
  • name: Endpoint name
  • summary: Endpoint summary from docstring

2. getEndpointDocs

Get detailed OpenAPI documentation for a specific endpoint.

Input:

  • endpoint_path (required): The path of the endpoint (e.g., "/users/{user_id}")
  • method (optional): The HTTP method (default: "GET")

Output: JSON object with detailed OpenAPI information including:

  • path: The endpoint path
  • method: The HTTP method
  • operation: OpenAPI operation details with fully resolved schemas

Transport Support

This library implements the latest MCP Streamable HTTP transport (protocol version 2025-03-26) which:

  • Uses a single HTTP endpoint for both requests and responses
  • Supports both immediate JSON responses and Server-Sent Events (SSE) streaming
  • Provides backward compatibility with older MCP clients
  • Includes proper session management with unique session IDs

Security

The library includes built-in security features:

  • Origin Header Validation: Prevents DNS rebinding attacks
  • CORS Configuration: Configured for localhost development by default
  • Session Management: Proper MCP session handling with unique IDs

For production use, make sure to:

  1. Configure appropriate CORS origins
  2. Implement proper authentication if needed
  3. Bind to localhost (127.0.0.1) for local instances

Integration with AI Agents

This library is designed to work with AI agents and MCP clients like:

  • Claude Desktop (via mcp-remote)
  • VS Code extensions with MCP support
  • Custom MCP clients

Example client configuration for VS Code Copilot:

{
  "mcpServers": {
    "your-api-name": {
      "url": "http://localhost:8000/mcp",
      "type": "sse",
      "dev": {
          "debug": {
              "type": "web",
          }
      }
    }
  }
}

Development

Setting up the development environment

git clone <repository-url>
cd fastapi-mcp-openapi
uv venv
source .venv/bin/activate
uv pip install -e ".[dev]"

Running tests

uv run pytest

# Coverage report (local)
uv run pytest --cov=fastapi_mcp_openapi --cov-report=html

Code Quality

This project uses several tools to maintain code quality:

# Run linting
ruff check .

# Auto-fix linting issues
ruff check . --fix

# Format code
ruff format .

# Type checking
mypy fastapi_mcp_openapi --ignore-missing-imports

Building the package

uv build

Publishing

See PUBLISHING.md for detailed instructions on setting up automated PyPI publishing with GitHub Actions.

Using locally built package

To use the locally built package in another FastAPI project, you can either install it from the wheel file or in editable mode.

# Option 1: Install from wheel file
pip install /path/to/fastapi_mcp_openapi-0.1.0-py3-none-any.whl
# or with uv
uv add /path/to/fastapi_mcp_openapi-0.1.0-py3-none-any.whl

# Option 2: Install in editable mode
pip install -e /path/to/fastapi-mcp-openapi
# or with uv
uv add --editable /path/to/fastapi-mcp-openapi

Example Applications

This repository includes two example applications in the examples/ folder demonstrating the library's features:

Simple Example (examples/simple_example.py)

A minimal example showing basic integration:

# Run the simple example
python examples/simple_example.py

This creates a basic FastAPI app with a few endpoints and shows the MCP integration info on startup.

Complete Example (examples/advanced_example.py)

A comprehensive example with multiple endpoint types, Pydantic models, and full CRUD operations:

# Run the complete example
python examples/advanced_example.py

Both examples can be seen in docs url at http://localhost:8000/docs after running the application.Use claude MCP inspector to see the MCP endpoints and tools. Connect to the MCP server at http://localhost:8000/mcp with transport type Streamable HTTP.

License

MIT License

Contributing

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

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