Fastmcp

FastMCP is the standard framework for building applications with the Model Context Protocol (MCP), which connects LLMs to tools and data. It provides everything you need to go from prototype to production: build servers that expose capabilities, connect clients to any MCP service, and give your tools interactive UIs. The framework is designed for Python developers who want to declare tools with simple functions, with automatic schema generation, validation, and documentation. FastMCP handles transport negotiation, authentication, and protocol lifecycle management, letting you focus on your logic. FastMCP has three pillars: Servers, Apps, and Clients. Servers wrap your Python functions into MCP-compliant tools, resources, and prompts. Apps give your tools interactive UIs rendered directly in the conversation (e.g., FastMCPApp, Interactive Tools, Generative UI, Custom HTML). Clients connect to any MCP server—local or remote—with full protocol support, either programmatically or via CLI. 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. It was incorporated into the official MCP Python SDK in 2024. FastMCP is made by Prefect and integrates with enterprise MCP gateway Horizon for production deployments with SSO, RBAC, audit logs, and more. Key features include automatic tool schema generation, OAuth support (Auth0, GitHub, Google, etc.), a Client-Only Package, multiple transports (stdio, SSE, HTTP), and a built-in CLI for server management. Recent releases added the fastmcp-remote bridge for stdio-only hosts and proactive token refresh for OAuth sessions. The project is open-source and free to use, with enterprise features available via Prefect Horizon.