Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does disclose substantive behavioral content: exactly which artifacts come back (SHA-256 of original and signed PDFs, signer/event records, positions in a public hash-chained log) and that an independent verification recipe is included. It stops short of stating the safety profile (read-only, no side effects) or any auth/rate-limit requirements.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.