Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes well beyond the readOnly/idempotent annotations: states the required scope (listings:read), enumerates what is returned (slugs, publication state, USD prices, edit links, nextCursor), explains paging termination (null ends the list), and describes the expired-token recovery path. This is the behavioral context an agent needs before calling.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.