Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the idempotentHint annotation, the description details exact behavioral outcomes for every enum value: 'off' still measures but never posts, 'preview' records without sending, 'public' never DMs, and human-required actions still ask for approval. It also discloses the team-admin permission requirement, all of which is valuable context not present in annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.