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Claude Code v2.1.280 ·

New classifier for rejected custom tool definitions

A new classifier sorts tool-definition errors into unsupported platform, disabled kind, or name conflict, and uses it to retry automatically

Group of 2 Under the hood Internal Changes
JSON All of v2.1.280
Under the hoodTier: how much it should matter to you
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2Signal: worth watching, 1 to 5
ElsewhereArea: what it touches
Internal ChangesKind: in v2.1.280,
Internal ChangesSection of the release

Unclear The finding doesn't say whether or how this classification is surfaced to end users versus used only internally.

What A new helper classifies 400/422 errors that mention a custom tool definition into one of three reasons:

  • unsupported_on_platform - the platform doesn't support tool definitions
  • kind_not_enabled - this kind of tool can't yet be defined in a message
  • name_conflict - the tool's name collides with an existing tool or addition

This classifier is used in the tool error-recovery retry path to decide whether to strip or downgrade a tool definition and retry the request. The feature is currently gated on the server side.

Why Instead of a custom tool definition failing outright, Claude Code can now recognize why it was rejected and automatically retry with an adjusted request in some cases.

How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtThe finding doesn't say whether or how this classification is surfaced to end users versus used only internally.

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