Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: the four phase values, the scoring-range rule ('closer than Polymarket when the top end is below 0'), that forecasts appear in their minute, that they may not count and why, and that format=concise drops the forecast rows. Pagination behavior when many forecasts exist is not disclosed, which keeps it from a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.