Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover read-only, idempotent, closed-world behavior, but the description adds real context: listing may be turned off for unauthenticated HTTP deployments, and entries carry creation/expiry time and a fetch-completeness flag. That is meaningful beyond the annotations, though permissions/error behavior is not discussed.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.