Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's useful addition is the return content: URL, last-checked date, section headings, and FAQ/card counts. With no output schema, that disclosure is genuinely valuable, though it says nothing about ordering, pagination, or what an empty result looks like.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.