Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, so the safety bar is low; the description adds real behavioral detail beyond them — the 50-result cap (default 20 is in the schema, the cap is not), the lone-category-word slug-browsing quirk, and the alias resolution table.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.