Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover read-only/idempotent/non-destructive, but the description adds real behavioral context beyond them: 'most recent available' is explicitly not necessarily today's, absence returns `found: false` rather than an error, and there is a subscription-tier precondition. These are exactly the surprises an agent would otherwise mis-handle.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.