Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds value by disclosing the returned content scope and the 'rolling' nature of the leaders data, but says nothing about data freshness limits, auth, or rate behavior. With annotations plus an output schema, this is adequate.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.