Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds value beyond that by disclosing the payload shape (all issues/violators/diagnoses in one response) and a size/cost caveat deferred to listIssues — a useful behavioral trait for a tool that may return very large payloads.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.