You'll noticeTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
Tool ValidationArea: what it touches
ImprovementsKind: in v2.1.277,
ImprovementsSection of the release
What
When a tool call fails validation, Claude Code builds an error message describing what went wrong, such as missing, unexpected, or wrong-type parameters. That message now also includes any custom validation error messages produced by the validation library (Zod) when a check is specifically marked as "custom".
Why
This surfaces more specific, tool-author-written explanations of why a call failed, instead of only generic parameter-shape errors.
