Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover safety (readOnly, non-destructive, idempotent). The description adds that it returns validity and format details, which is useful but does not disclose limitations such as not checking real-world existence or handling of whitespace/case. No contradiction with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.