Your tests only cover the happy path, so they pass until production, where tools time out and APIs return half a response. Chaos testing checks what your agent does when a tool returns a wrong but plausible value, like 12 degrees for Miami in June, buried in a verbose dump. The agent reports it as fact and burns tokens reading the junk. A small guardrail range-checks the value and replaces a bad result with a one-line error before the model ever sees it, fixing both accuracy and token cost.

Outline:
• The happy-path trap
• Inject realistic corruption
• The guardrail that catches it
• One run is not a measurement
• Build chaos into your test suite