mcp-it 0.1.1

Transform any FastAPI server into an MCP server

mcp-it

Transform any FastAPI server into an MCP (Model Context Protocol) server.

mcp-it allows you to seamlessly convert your FastAPI routes into MCP tools. Decorate your FastAPI endpoints with @mcp_it.mcp() and your API becomes an MCP server that can be used with MCP-compatible clients.

Features

• Minimal Code Changes: Convert existing FastAPI routes to MCP tools with a simple decorator
• Automatic Parameter Detection: Automatically detects path, query, and body parameters from your FastAPI routes - no boilerplate reimplementation
• Header Forwarding: Maps and preserves headers from MCP requests to your FastAPI endpoints
• Dependency Injection: Full support for FastAPI's dependency injection system
• Pydantic Models: Full integration with Pydantic models for request/response validation
• Multiple Transports: Support for both sse and streamable-http transports
• Type Safety: Maintains type hints and annotations for proper MCP tool introspection
• Auto Docs: Automatically documents the MCP tools with your functions docstrings

Installation

pip install mcp-it

Quick Start

from fastapi import FastAPI, APIRouter
from mcpit import MCPIt

# Create your FastAPI app
app = FastAPI()

# Initialize MCPIt
mcp_it = MCPIt("My API Tools", json_response=True)

# Decorate your routes with @mcp_it.mcp()
@app.post("/multiply")
@mcp_it.mcp(mode='tool', description="Multiply two numbers")
def multiply(a: float, b: float):
    """Multiplies two numbers together."""
    return {"result": a * b}

# Build and mount the MCP server
mcp_it.build(app.router, transport='streamable-http', mount_path="/mcp")

# Your MCP server is now available at /mcp

Usage

Basic Example

from fastapi import FastAPI, APIRouter
from mcpit import MCPIt
from pydantic import BaseModel, Field

app = FastAPI()
router = APIRouter()
mcp_it = MCPIt("Calculator Tools", json_response=True)

class CalculationInput(BaseModel):
    a: float = Field(..., description="The first number")
    b: float = Field(..., description="The second number")

@router.post("/add")
@mcp_it.mcp(mode='tool', name="add", description="Add two numbers")
def add(input: CalculationInput):
    """Adds two numbers together."""
    return {"result": input.a + input.b}

mcp_it.build(router, transport='streamable-http', mount_path="/mcp")
app.include_router(router)

With Authentication

mcp-it automatically forwards headers from MCP requests, so your authentication dependencies work seamlessly:

from fastapi import Header, Depends
from typing import Optional

def fake_auth_dependency(authorization: Optional[str] = Header(None)):
    """Validate authorization header"""
    if authorization:
        return True
    return False

@router.get("/protected")
@mcp_it.mcp(mode='tool', description="Protected endpoint")
def protected_route(auth_result: bool = Depends(fake_auth_dependency)):
    """A protected route that requires authentication."""
    return {"message": "Access granted", "authenticated": auth_result}

With Dependency Injection

Full support for FastAPI's dependency injection:

class BasicService:
    def __init__(self):
        self.counter = 0
    
    def increment(self) -> int:
        self.counter += 1
        return self.counter

service = BasicService()
def get_service() -> BasicService:
    return service

from typing import Annotated
from fastapi import Depends

ServiceDep = Annotated[BasicService, Depends(get_service)]

@router.get("/increment")
@mcp_it.mcp(mode='tool', description="Increment counter")
def increment(service: ServiceDep):
    """Increment the counter using dependency injection."""
    return {"count": service.increment()}

Path and Query Parameters

mcp-it automatically detects and handles path and query parameters:

@router.get("/users/{user_id}/posts")
@mcp_it.mcp(mode='tool', description="Get user posts")
def get_user_posts(user_id: int, limit: int = 10, offset: int = 0):
    """Get posts for a specific user with pagination."""
    return {
        "user_id": user_id,
        "posts": [],
        "limit": limit,
        "offset": offset
    }

API Reference

MCPIt

The main class for creating MCP servers from FastAPI routes.

Constructor

MCPIt(name: str, json_response: bool = True)

• name: Name of your MCP server
• json_response: Whether to return JSON responses (default: True)

Methods

mcp(mode='tool', **kwargs)

Decorator to register a FastAPI route as an MCP capability.

Parameters:

• mode: Type of MCP capability ('tool', 'resource', or 'prompt')
• name: (optional) Custom name for the tool (defaults to function name)
• description: (optional) Tool description (defaults to function docstring)

Example:

@mcp_it.mcp(mode='tool', name="custom_name", description="Custom description")
def my_function():
    pass

build(router, transport='streamable-http', mount_path='/mcp')

Builds the MCP server and mounts it to your FastAPI router.

Parameters:

• router: Your FastAPI APIRouter instance
• transport: Transport type ('sse' or 'streamable-http')
• mount_path: Path where the MCP server will be mounted (default: /mcp)

Example:

mcp_it.build(router, transport='streamable-http', mount_path="/mcp")

How It Works

1. Decorator Registration: When you use @mcp_it.mcp(), the function is registered in an internal registry
2. Route Analysis: During build(), mcp-it analyzes your FastAPI routes to detect:
   • Path parameters
   • Query parameters
   • Body parameters
   • Pydantic models
3. Tool Creation: MCP tools are created with proper signatures and type annotations
4. Internal Proxy: When an MCP tool is called, mcp-it makes an internal ASGI call to your FastAPI route
5. Header Forwarding: Headers from MCP requests are automatically forwarded to your endpoints

Transport Modes

Streamable HTTP (Recommended)

mcp_it.build(router, transport='streamable-http', mount_path="/mcp")

• Uses HTTP with streaming support
• Better for production environments
• Supports all HTTP methods

SSE (Server-Sent Events)

mcp_it.build(router, transport='sse', mount_path="/mcp")

• Uses Server-Sent Events for streaming
• Good for real-time updates
• Simpler connection model

Development

Setup

# Clone the repository
git clone https://github.com/enzobjmendonca/mcp-it.git
cd mcp-it

# Install development dependencies
pip install -r requirements.txt

# Install the package in editable mode
pip install -e .

Running Tests

pytest

Examples

See the example.py file in the repository for a complete working example with:

• Multiple route types
• Pydantic models
• Authentication
• Dependency injection
• Path and query parameters

Requirements

• Python 3.8+
• FastAPI
• FastMCP
• httpx
• Pydantic

Contributing

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

License

MIT License - see LICENSE file for details.

Links

• GitHub: https://github.com/enzobjmendonca/mcp-it
• PyPI: https://pypi.org/project/mcp-it
• Issues: https://github.com/enzobjmendonca/mcp-it/issues