FastMCP — Python Framework for MCP Servers

Main

• Start from the minimal server example, then move each tool into small, testable Python functions with clear docstrings.

• Keep tool contracts stable: treat schemas and return types as an API, and version changes in your MCP server like any other service.

• Add production concerns early (timeouts, rate limits, auth) and keep a staging server to validate client compatibility.

• Use the project docs links for server/client/app patterns instead of inventing protocol glue by hand.

README (excerpt)

FastMCP 🚀

Move fast and make things.

Made with 💙 by Prefect

The Model Context Protocol (MCP) connects LLMs to tools and data. FastMCP gives you everything you need to go from prototype to production:

from fastmcp import FastMCP

mcp = FastMCP("Demo 🚀")

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

if __name__ == "__main__":
    mcp.run()

Why FastMCP

Building an effective MCP application is harder than it looks. FastMCP handles all of it. Declare a tool with a Python function, and the schema, validation, and documentation are generated automatically. Connect to a server with a URL, and transport negotiation, authentication, and protocol lifecycle are managed for you. You focus on your logic, and the MCP part just works: with FastMCP, best practices are built in.

Source-backed notes

• README shows a minimal server using FastMCP("Demo"), a @mcp.tool function, and mcp.run().
• README recommends installing via uv pip install fastmcp and links to a dedicated docs site.
• Project description frames FastMCP as a higher-level way to build MCP servers/clients without manual schema wiring.

FAQ

• Is FastMCP a server or a client?: README describes both server and client patterns; start by building a server first.
• Do I need uv?: README recommends uv, but pip-based installs are also common for Python libraries.
• How do I keep tool behavior predictable?: Treat tool schemas as an API contract, add tests, and version breaking changes.