Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish readOnly, idempotent, non-destructive and closed-world behavior, so the bar is lower, and the description still adds real semantics beyond them: the newest-first ordering, the non-obvious aggregation rule (one author's consecutive changes within 10 minutes collapse to a single version), and the permission-based visibility rule. It omits pagination/limit behavior, but the added behavioral context is substantive.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.