{"version":"2.1.257","anchor":"new-400-error-classification-for-tool-additiontool-removal","canonical_anchor":"new-400-error-classification-for-tool-additiontool-removal","heading":"New 400-error classification for tool_addition\/tool_removal API errors","tier":"internal","area":"Tools","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.257\/e\/new-400-error-classification-for-tool-additiontool-removal","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.257","markdown":"### New 400-error classification for tool_addition\/tool_removal API errors\n\nRejected mid-conversation tool additions are now sorted into specific 400-error reasons for retry and telemetry.\n\nNew internal classification logic sorts 400 errors from beta tool-use blocks into specific reasons: `header_rejected`, `block_type_unknown`, `after_paused_turn`, `model_unsupported`, `too_many_definitions`, `pfc_only`, `unknown_tool_reference`, or `other`. This applies when a `tool_addition` or `tool_removal` request is rejected, likely feeding retry and telemetry logic for beta feature flags.\n\n- Area: Tools\n- Names: `header_rejected`, `model_unsupported`, `too_many_definitions`\n- Tier: Under the hood\n- Useful: 2\/5\n- Signal: 3\/5"}