Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It usefully discloses that the operation is 'Read-only' and 'Recomputable from public chain data + the public mandate,' implying deterministic, no-secret-state behavior. It does not, however, cover error/permission cases or what happens if no mandate is committed, leaving real gaps for a verification tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.