Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so much of the behavioral burden is lifted. The description adds that only the 'public' object is returned, which is useful scope information not in annotations, but doesn't discuss errors for missing ids, permissions, or rate limits.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.