This tutorial walks you through building a complete MCP server in Python. 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