Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and closed-world. The description adds real context beyond them: it returns closed offers rather than erroring, and it flags the closed state, which an agent could not infer from the annotations. The linking instruction is presentational rather than behavioral, so it isn't a full 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.