FastMCP

Pricing

• Free and open source (Apache-2.0)

Install

uv add fastmcp

pip install fastmcp

pip install "fastmcp[tasks]"

Models

Model-agnostic: FastMCP is a Python framework for building MCP servers and clients, and any MCP-compatible client can call the servers it produces. FastMCP 4 runs on the rewritten MCP Python SDK v2 and the 2026-07-28 protocol revision, negotiating the best protocol version per connection.

Recent changes

• Oct 16v3.4.9 backports 4.1 security fixes to the 3.x line: OpenAPI path parameters reject . and .. segments, SKILL.md files must stay inside their skill folder, and regex tool search is bounded in time and pattern length.
• Oct 8v4.1.0 is a broad fix release with full Python 3.15 support. Breaking changes include HTTP sessions expiring after the SDK's 30-minute idle default, source-qualified MultiAuth client IDs, and Pydantic's regex engine for tool search.
• Aug 31FastMCP 4.0.0 goes stable on MCP Python SDK v2, adding interactive tools, background tasks, a server extension API and argument completion. It removes server-initiated sampling and roots, and moves background tasks into fastmcp-tasks.

Sources: FastMCP installation docs, GitHub releases, v4.0.0 release notes, LICENSE

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