FastMCP

FastMCP is the standard framework for building Model Context Protocol (MCP) applications in Python. Created by Jeremiah Lowin and maintained by Prefect, it lets you wrap any Python function into an MCP-compliant tool with automatic schema generation, validation, and documentation. The framework operates on three pillars: Servers for exposing tools, resources, and prompts to LLMs; Apps for giving tools interactive UIs rendered directly in conversations; and Clients for connecting to any MCP server locally or remotely. Getting started takes seconds. Decorate a function with @mcp.tool, run the server, and you have a fully compliant MCP endpoint. No manual schema definitions, no boilerplate. FastMCP handles transport negotiation (stdio, SSE, streamable-http), authentication, and the entire protocol lifecycle. FastMCP 1.0 was incorporated into the official MCP Python SDK in 2024. The standalone project (now at v3.2.4) is downloaded over a million times per day and powers roughly 70% of all MCP servers across every programming language. That is not a typo: seven out of ten MCP servers in production use some version of FastMCP. For production deployments, Prefect Horizon provides an enterprise MCP gateway with SSO, tool-level RBAC, audit logs, branch previews, and instant rollback. The open-source framework itself is Apache-2.0 licensed and free to use. Who should use FastMCP? Any developer building MCP servers or clients, whether you are wrapping an internal API, creating a tool for Claude Code, or building a multi-agent system. The framework handles the MCP protocol details so you can focus on your business logic.