Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already carry the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower; the description still adds account scoping, the authentication mechanism and exact header format. It doesn't mention pagination limits or rate limits beyond the schema's 'limit' field.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.