Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description still adds genuinely non-obvious behavior: the call returns a free sample plus paid URL and pay steps without charging, while the full result costs $0.01 Base USDC via x402. It stops short of stating rate limits or what the sample omits.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.