Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare this is a read-only, non-destructive, closed-world operation, and the description adds useful behavioral context: it lists all classifications and returns bilingual names and IDs. It does not describe ordering or pagination, but those are minor for a small static reference list.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.