Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish that this is a read-only, non-destructive, closed-world operation. The description adds useful behavioral context: the listed reports compare the last 28 full days with the previous 28 days, and their requests can be passed directly to run_report.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.