Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already flag read-only, idempotent, non-destructive behavior, so the description doesn't need to restate those. It adds behavioral context beyond annotations by listing the metric categories, noting that personal email providers are filtered in the organization domains metric, and restricting scope to the agent's own published briefings.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.