Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the annotations (readOnly/idempotent/non-destructive), it discloses owner scoping, an entitlement tier with rejection behavior, and the empty-state contract (empty list plus all-zero summary is valid, not an error). These are exactly the non-obvious behaviors an agent needs before calling.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.