Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered. The description adds pagination behavior (25 default, 200 max, ~64 KB budget, short pages with next_cursor), cursor semantics ('absence means you have the last page'), and unknown-tag behavior ('comes back with the topics that do exist'). These are meaningful behavioral details beyond annotations, with no contradiction.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.