Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover readOnly=false, non-idempotent, and non-destructive. The description adds non-obvious behavioral context: 'this server holds no keys, no funds and no tokens', 'Free with a valid signature', and that it returns the recorded offer and token terms. This goes beyond annotation-only information.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.