Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds beyond that: the $0.25 USDC payment requirement, the GET endpoint using x402 on Base, and the returned data fields. This enriches the agent's understanding of cost and API usage.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.