Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds valuable context: the data is scoped to the authenticated user, and it covers daily/monthly periods and tier limits. This goes beyond the annotations and clarifies the snapshot nature of the resource.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.