Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly true, destructive false, openWorld false), so the bar is lower; the description still adds real behavioral context — the value space for each row (state, flow, acceleration), the CSV-per-day granularity, and the access-scoped depth constraint. The closing caveat that readings are measurements, not predictions or recommendations, further clarifies semantics.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.