Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint and idempotentHint. The description adds value by clarifying the output item shape: each item has a JID, a phone number stored in 'name', and an 'admin' flag. It does not mention pagination or error behavior, but the output schema covers return values.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.