Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, openWorldHint=false. The description adds useful context: the limit of 100 rows, the interpretation of absence (not untrustworthy), and the lack of commercial rating/ranking. This goes beyond the safety profile to clarify data semantics.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.