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fastmcp

PrefectHQ/fastmcp

Fast, Pythonic way to build MCP servers and clients

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Python Apache-2.0Created Nov 30, 2024

Overview

FastMCP is a framework that connects LLMs to tools and data via the Model Context Protocol (MCP). It simplifies building applications by handling server-side operations such as schema generation, validation, documentation, and protocol lifecycle management.

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README

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.

That's why FastMCP is the standard framework for working with MCP. FastMCP 1.0 was incorporated into the official MCP Python SDK in 2024. Today, the actively maintained standalone project is downloaded a million times a day, and some version of FastMCP powers 70% of MCP servers across all languages.

FastMCP has three pillars:

Servers
Expose tools, resources, and prompts to LLMs.

Apps
Give your tools interactive UIs rendered directly in the conversation.

Clients
Connect to any MCP server — local or remote, programmatic or CLI.

Servers wrap your Python functions into MCP-compliant tools, resources, and prompts. Clients connect to any server with full protocol support. And Apps give your tools interactive UIs rendered directly in the conversation.

Ready to build? Start with the installation guide or jump straight to the quickstart.