Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so safety is covered structurally. The description adds value beyond annotations by disclosing the 50-result cap, the opaque-cursor continuation model, and the bounded wait with a 30-second maximum. No contradiction with annotations. Minor gap: it does not state what happens when the wait expires with no new message.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.