PrefectHQ/FastMCP
🚀 The fast, Pythonic way to build MCP servers and clients.
FastMCP is the most popular Python framework for building Model Context Protocol (MCP) servers and clients, maintained by Prefect. It turns any Python function into an MCP tool with a decorator, then deploys it so AI agents like Claude can call it. FastMCP 1.0 became part of the official MCP SDK.
Our Review
With more than 25,000 GitHub stars and near-daily releases (v3.4.1 shipped in June 2026), FastMCP is the de facto standard for building MCP servers in Python. Its 1.0 version was contributed to the official MCP Python SDK, and FastMCP 2.0 and beyond, maintained by Prefect, is the actively developed framework most servers are built on today.
What FastMCP does:
- •Decorator-based tools turn any Python function into an MCP tool, resource, or prompt by adding a decorator, with types and docs handled for you.
- •Servers and clients build both MCP servers and the clients that call them from one library.
- •Production features authentication, deployment helpers, middleware, and testing utilities to go from prototype to production.
- •Proxy and compose proxy existing MCP servers and compose several into one, useful for building gateways.
- •Generate from existing APIs turn an OpenAPI spec or a FastAPI app into an MCP server automatically.
- •Multiple transports run over stdio, HTTP, or SSE so the same server works with different clients.
FastMCP ecosystem:
- •Official MCP SDK FastMCP 1.0 is part of the official Model Context Protocol Python SDK.
- •Claude and other clients servers you build work with Claude Desktop, Claude Code, and any MCP-compatible client.
- •Docs at gofastmcp.com full guides plus an active Discord community.
Getting started:
Install with pip install fastmcp, define a server with FastMCP("My Server"), decorate a function with @mcp.tool, and run it. Point Claude Desktop or Claude Code at the server and your function becomes a callable tool. Full docs and examples are at gofastmcp.com.
Limitations:
FastMCP is a Python developer framework, so building servers means writing and hosting code rather than installing a finished tool. The MCP ecosystem moves quickly, and with 250+ open issues and a fast release pace, occasional breaking changes between major versions do happen. It targets Python specifically, so teams on other languages need a different MCP SDK. The framework builds servers but does not host them for you.
Our Verdict
FastMCP is the default way to build MCP servers in Python in 2026, and its decorator API is what makes exposing a tool to an AI agent take a few lines instead of a full protocol implementation.
For Developers, FastMCP is the fastest path to giving an AI agent new capabilities: wrap your function, run the server, and Claude or any MCP client can call it with full type information. The OpenAPI and FastAPI generators mean you can turn an existing API into an agent-ready tool quickly.
For Vibe Builders, FastMCP is the layer under many of the MCP servers you might install, so you would reach for it when you want to build a custom tool rather than use an existing one. It does require Python, so it sits a step beyond no-code.
Skip it if you only want to use existing MCP servers rather than build your own, or if your stack is not Python, where an SDK for your language fits better. For anyone building MCP tools in Python, though, FastMCP is the standard choice, backed by Prefect.
Frequently Asked Questions
Is FastMCP free and open-source?
Yes, FastMCP is free and open-source under the Apache 2.0 license, and it has more than 25,000 GitHub stars as of 2026. It is maintained by Prefect, the workflow-orchestration company. You can build and run MCP servers with it at no cost, paying only for any infrastructure you choose to host them on.
What is FastMCP used for?
FastMCP is used to build Model Context Protocol servers and clients in Python. It turns Python functions into MCP tools, resources, and prompts with decorators, so AI agents and assistants like Claude can call your code. It can also generate MCP servers automatically from existing OpenAPI specs or FastAPI applications.
What is the Model Context Protocol (MCP)?
The Model Context Protocol is an open standard that connects large language models to external tools and data sources in a consistent way. FastMCP is a Python framework that implements this protocol, making it simple to expose your own tools to MCP-compatible clients such as Claude Desktop and Claude Code.
What is the difference between FastMCP and the official MCP SDK?
FastMCP 1.0 was contributed to and became part of the official Model Context Protocol Python SDK. FastMCP 2.0 and later, maintained by Prefect, is a separate and more full-featured framework with added production features like authentication, proxying, and testing. Choose FastMCP for the richer toolset; the official SDK covers the protocol basics.
Can FastMCP servers work with Claude?
Yes, MCP servers built with FastMCP work with any MCP-compatible client, including Claude Desktop and Claude Code. You point the client at your running server and its tools become available to the assistant. FastMCP also supports multiple transports, including stdio and HTTP, so the same server works across different clients.
What is FastMCP?
FastMCP is the most popular Python framework for building Model Context Protocol (MCP) servers and clients, maintained by Prefect. It turns any Python function into an MCP tool with a decorator, then deploys it so AI agents like Claude can call it. FastMCP 1.0 became part of the official MCP SDK.
How do I install FastMCP?
Visit the GitHub repository at https://github.com/PrefectHQ/fastmcp for installation instructions.
What license does FastMCP use?
FastMCP uses the Apache-2.0 license.
What are alternatives to FastMCP?
Explore related tools and alternatives on My AI Guide.
Open source & community-verified
Apache-2.0 licensed: free to use in any project, no strings attached. 25,511 developers have starred this, meaning the community has reviewed and trusted it.
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