API type mismatch silently broke 107 of 121 agent tool chains for months

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A helpdesk platform discovered that its AI agent API had a critical type mismatch: ticket IDs were returned as integers but the input schema required strings, causing validation failures whenever an agent passed an ID from one tool directly into another. An audit revealed all 24 ID-emitting fields returned numbers while all 14 ID-accepting fields demanded strings, breaking 107 out of 121 possible tool chains. The bug went undetected for months because the test suite used defensive String() casts that mimicked careful human input rather than the literal output an AI agent would pass. Compounding the problem, the API's own documentation instructed agents to use IDs exactly as returned, actively directing them into the failure. The team resolved the issue by adding a guarded preprocessor that silently coerces only valid positive integers to strings, leaving the published JSON Schema contract unchanged.

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