FastMCP+ FastAPI Integration

fastmcp-fastapi.py

from fastapi import FastAPI
from starlette.routing import Mount, Route
from mcp.server import FastMCP
from mcp.server.sse import SseServerTransport

mcp = FastMCP("MCP")

sse = SseServerTransport("/messages/")

async def handle_sse(request):
    async with sse.connect_sse(
        request.scope, request.receive, request._send
    ) as streams:
        await mcp._mcp_server.run(
            streams[0],
            streams[1],
            mcp._mcp_server.create_initialization_options(),
        )

app = FastAPI(
    title="FastAPI + FastMCP Server",
    description="",
    version="0.1.0",
    routes=[
        Route("/sse", endpoint=handle_sse),
        Mount("/messages/", app=sse.handle_post_message),
    ]
)


@app.get("/demo")
async def api_call(id: str):
    return f"API returned id={id}"

@mcp.tool()
async def mcp_call(id: str) -> str:
  """Simple MCP tool"""
  return await api_call(id)


# Run FastAPI and MCP server with the command: `fastapi run demo.py --port 3001`
# The API docs is available at `http://localhost:3001/docs`
# The MCP SSE endpoint is available at `http://localhost:3001/sse`
# In other terminal, you can inspect the MCP with the command `mcp dev demo.py`, then visit `http://localhost:5173/#tools`

# Run **only** the MCP server via STDIO with the command: `uv run --with mcp mcp run demo.py`
# Run FastAPI and MCP server via STDIO with the command: `uv run --with fastapi fastapi run demo.py --port 3001`