Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, and closed-world behavior, so the safety profile is covered. The description adds useful behavior beyond that: the output is large, and coverage explicitly separates what is documented here from what must be checked in official documentation. It does not describe the return shape in detail, but the listed sections give a reasonable preview.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.