This tutorial walks you through building a complete MCP server in Python. For Python environment, async, validation, and production patterns around AI services, use the Python for AI developers guide. For the TypeScript version, see our TypeScript tutorial.

Install

pip install mcp httpx

Create the server

from mcp.server import Server
from mcp.server.stdio import stdio_server
import httpx

server = Server("my-dev-tools")

@server.tool()
async def check_website(url: str) -> str:
    """Check if a website is responding and measure latency."""
    try:
        async with httpx.AsyncClient() as client:
            response = await client.get(url, timeout=10)
            return f"{url}: {response.status_code} ({response.elapsed.total_seconds():.2f}s)"
    except Exception as e:
        return f"{url}: UNREACHABLE — {str(e)}"

@server.tool()
async def count_lines(file_path: str) -> str:
    """Count lines in a file."""
    try:
        with open(file_path) as f:
            count = sum(1 for _ in f)
        return f"{file_path}: {count} lines"
    except FileNotFoundError:
        return f"File not found: {file_path}"

Add the transport

import asyncio

async def main():
    async with stdio_server() as (read, write):
        await server.run(read, write, server.create_initialization_options())

if __name__ == "__main__":
    asyncio.run(main())

Connect to Claude Code

claude mcp add my-tools python /path/to/server.py

Connect to Claude Desktop

Add to config:

{
  "mcpServers": {
    "my-tools": {
      "command": "python",
      "args": ["/absolute/path/to/server.py"]
    }
  }
}

Using FastMCP (simpler API)

pip install fastmcp

from fastmcp import FastMCP

mcp = FastMCP("my-server")

@mcp.tool()
def add(a: int, b: int) -> int:
    """Add two numbers."""
    return a + b

mcp.run()

FastMCP handles transport, error handling, and type validation automatically.

Security

Always validate inputs and handle errors. See our MCP Security Checklist for production guidelines.

Related: Build MCP Server (TypeScript) · What is MCP? · Best MCP Servers · MCP Complete Guide