Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds meaningful behavioral/access context beyond annotations: the call costs $0.10, supports prepaid x-credit-token headers, includes a free tier, needs no wallet or API key, and returns an auditable receipt.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.