Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, non-destructive, closed-world), so the bar is lower. The description earns credit by disclosing the content shape (actual/forecast/previous, surprise direction, measured reaction in the minutes after release) and that results default to high-impact releases, with archive coverage disclosed via a parameter — substantive behavioral context beyond the annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.