Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds the useful behavioral context that the events are 'private' and 'hash-only,' which indicates access restrictions and content type. It does not contradict annotations, but it also does not disclose any other operational traits such as pagination or ordering.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.