Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does disclose a meaningful behavioral trait: the call costs $0.02 in USDC via x402, plus the shape of the returned payload. However, it says nothing about the payment flow — whether payment is required before the call, what happens on insufficient funds, or error/retry behavior — which matters for a paid endpoint.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.