Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations available, the description carries the full burden and does so well: it explains what `ok=true` means, that unsigned receipts fail, that a passing verification does not prove signer identity, and that post-quantum keys are not covered by the `kid`. These are exactly the behavioral caveats an agent needs before relying on the result.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.