v4.21.2
punkpeye/fastmcpv4.21.2Sep 25, 2026by github-actions[bot]
Upgrading?
AI Summary
Focuses on refining tool input schemas and error handling. It fixes errors for unknown resources, ensures free-form arguments are handled correctly, and improves security by hiding unauthorized tools.
Key Highlights
- Fixes error code -32602 for unknown prompts/resources in completion
- Ensures free-form object arguments remain open in advertised tool inputs
- Hides canAccess tools from sessions that failed authentication
- Fixes record value schemas in advertised tool inputs
Full Release Notes
## [4.21.2](https://github.com/punkpeye/fastmcp/compare/v4.21.1...v4.21.2) (2026-09-25) ### Bug Fixes * answer -32602 when completion/complete names an unknown prompt or resource template ([f05b026](https://github.com/punkpeye/fastmcp/commit/f05b026e20ddb60703066f879d8a0d7ee3d0c18a)) * **edge:** keep record value schemas in advertised tool inputs ([d214e31](https://github.com/punkpeye/fastmcp/commit/d214e313b268fc103cc730d1edd385e5998647d0)) * hide canAccess tools from sessions that failed to authenticate ([28cdac4](https://github.com/punkpeye/fastmcp/commit/28cdac4b90c6bd9718a33b27030eb57445266fc8)) * keep free-form object arguments open in advertised tool inputs ([4a3b84d](https://github.com/punkpeye/fastmcp/commit/4a3b84d658736b5982be96e3e5f61349e77ca635))
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