Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations only flag it as a non-read-only, non-idempotent, non-destructive open-world call; the description adds the economically critical behavior an agent cannot infer: credits are spent, the charge is capped at the quote, unused credits are released, the quote is single-use and time-boxed. It does not contradict the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.