Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, but the description goes further: it states no evaluation budget is consumed, nothing is sent or fired, no webhook URL or credential is exposed, and it is not counted on the caller's key. It also flags that `history` is a past-fact projection (would have fired in the last 30 days), which prevents a common misinterpretation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.