Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond them by disclosing the owner-only access constraint, the exact status enum values, and the three concrete pieces of data returned (in-flight version, reviewer's needs-changes reason, security-scan findings with severity). It also pre-empts the obvious safety question by stating READ-ONLY outright.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.