v4.22.1
biomejs/biomev4.22.1Sep 30, 2026by github-actions[bot]
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AI Summary
This is a patch release for FastMCP that fixes bugs related to handling unknown tools, initializing with the correct protocol version, and managing OpenAPI GET requests with referenced array parameters.
Key Highlights
- Fixed error code (-32602) for unknown tools and resources
- Fixed initialization handshake to use client's protocol version
- Fixed OpenAPI handling to keep GET requests with referenced array parameters
New Features
- Improved error handling for unknown tools
- Fixed protocol version negotiation
- Corrected OpenAPI parameter handling
Full Release Notes
## [4.22.1](https://github.com/punkpeye/fastmcp/compare/v4.22.0...v4.22.1) (2026-09-30) ### Bug Fixes * answer -32602 for an unknown tool or resource ([#406](https://github.com/punkpeye/fastmcp/issues/406)) ([3cc03cf](https://github.com/punkpeye/fastmcp/commit/3cc03cfea6ca74dd5b0c004de498a3083e8f2348)) * **edge:** answer initialize with the client's protocol version ([#403](https://github.com/punkpeye/fastmcp/issues/403)) ([da0c026](https://github.com/punkpeye/fastmcp/commit/da0c026916fc31976123cdc7e86f88d74c8e14a7)) * **openapi:** keep GETs with referenced array parameters as tools ([#405](https://github.com/punkpeye/fastmcp/issues/405)) ([14e4883](https://github.com/punkpeye/fastmcp/commit/14e4883ce902f773566c72297d7ccf735a1ac6b8))
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