Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true and readOnlyHint=false, but the description adds genuinely non-obvious behavior: there is no true group-delete, so the call empties the group and exits, plus an admin authorization requirement. The main gap is failure semantics — nothing says what happens if a member removal fails mid-way or if the caller is not an admin.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.