{"version":"2.1.221","anchor":"tool-search-refused-for-pre-4-5-models-on-vertex","canonical_anchor":"tool-search-refused-for-pre-4-5-models-on-vertex","heading":"Tool search refused for pre-4.5 models on Vertex","tier":"notice","area":"MCP","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.221\/e\/tool-search-refused-for-pre-4-5-models-on-vertex","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.221","markdown":"### Tool search refused for pre-4.5 models on Vertex\n\nFixes older Vertex models erroring on tool search; they now just load MCP tools normally.\n\n**What**\n\nVertex-served older models rejected the tool-search beta header; those sessions now fall back to loading MCP tools normally instead of deferring them behind ToolSearch.\n\n**Details**\n\n- applies only when the provider is vertex, and matches claude-3* models plus opus\/sonnet\/haiku models outside generations 4 and 5\n- short-circuits the tool-search capability check with reason `vertex_model_unsupported`\n- the same check is applied at the MCP-deferral, tool-search-tool-injection and headless MCP prewait call sites\n- the periodic tool-search reminder is suppressed for those models\n\n**Evidence**\n\n`Tool search disabled for model '${e}' on Vertex: this model's Vertex serving stack rejects the tool-search beta header (pre-4.5 generation).`, `this model's Vertex serving stack rejects the tool-search beta header (pre-4.5 generation).`\n\n- Area: MCP\n- Tier: You'll notice\n- Useful: 4\/5\n- Signal: 0\/5"}