Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover read-only/idempotent/no-destruction, and the description adds genuinely non-obvious context: no auth required, hidden picks are dropped so 'total' reflects only visible posts, and results are returned as summaries. It does not discuss rate limits, but the added visibility and auth semantics go well beyond the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.