Tool Manifest Lies: When Your Agent Trusts a Schema Your Backend No Longer Honors
The most dangerous bug in a production agent isn't the one that throws. It's the one where a tool description says returns user_id and the backend quietly started returning account_id two sprints ago, and the model is still happily inventing user_id in downstream reasoning — because the manifest said so, and the few-shot history reinforced it, and nothing in the loop ever fetched ground truth.
This is manifest drift: the slow, silent divergence between what your tool descriptions claim and what your endpoints actually do. It rarely produces stack traces. It produces bad decisions with clean audit trails — the worst class of bug in agent systems.
