Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is clear. The description adds valuable context beyond annotations by specifying the categories of metadata returned (filters, groupings, metrics, detail fields, citation fields), which helps the agent know what to expect without contradicting the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.