Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=true, so the description correctly adds value by detailing the exact output fields (JID, phone number in 'name', 'admin' flag) without contradicting the read-only nature. It doesn't disclose potential limitations like pagination, but for a simple list operation this is sufficient.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.