Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description is free to add behavior it alone can supply: the 15,000-character cap and the meaning of `bodyTruncated: true`, plus the recommended recovery action. That is real added context, though it doesn't say what happens for missing/inaccessible pageIds.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.