Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds meaningful semantics beyond them: that the payload carries cached links, relationship basis, timestamps and 'missing' checks, and that a not_available status is not evidence of closure. It still omits default section behavior and any limits on the response.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.