Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes well beyond annotations: it documents the state machine (only DRAFT/SCHEDULED accepted, all other statuses 400), the 404 workspace-scoping rule, and the idempotency semantics ('safe to repeat on a post that is already an undated draft'). It also reassures that nothing publishes, which reconciles the destructiveHint=true flag with what is actually lost (only the scheduled date).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.