FastMCP

FastMCP is a Python framework designed for building servers, clients, and applications that use the Model Context Protocol (MCP). MCP connects large language models (LLMs) to external tools and data sources, and FastMCP automates many of the underlying complexities. It handles schema generation, input validation, documentation, transport negotiation, authentication, and protocol lifecycle management automatically, allowing developers to focus on defining tool logic with standard Python functions. The framework is organized into three pillars: Servers (expose tools, resources, and prompts to LLMs), Clients (connect to any MCP server with full protocol support), and Apps (which add interactive user interfaces that render directly within the conversation). FastMCP 1.0 was incorporated into the official MCP Python SDK in 2024, and the actively maintained standalone project powers a significant majority of MCP servers across all programming languages, with high daily download numbers. The tool is developed by the team at Prefect and is closely related to Prefect Horizon, an enterprise MCP gateway for running FastMCP servers in production with additional security, governance, and observability features.