Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, closed-world, non-destructive, so safety needs no restating. The description goes beyond them by disclosing the fallback behavior for unrecognized trades and by scoping out pricing/budget content, which tells the agent what the response will and will not contain.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.