Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the safety profile (readOnly, non-destructive, non-idempotent, closed-world), so the bar is lower. The description adds real context beyond that: ordering ('newest first'), per-response payload contents, and an ownership/authorization constraint ('only works for forms the user owns').
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.