Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds genuinely non-obvious behavior: the fallback rule when current_time.timezone_resolved is false (report as UTC, never local) and the provenance of solar data via the weather pipeline's astro product.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.