Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover read-only/idempotent/non-destructive behavior, so the description's job is lighter. It adds useful context: no auth required, data source, 2000+ categories, and the exact returned fields (id, title, parent_id, taxonomy path). It does not mention pagination or rate limits, which would have pushed it higher.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.