Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden. It adds valuable behavioral context: 402 is a payment instruction, credits land ~1 block after payment, and the nonce must be preserved. It does not mention auth or rate limits, but the protocol-specific nuance is well disclosed.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.