Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful beyond-annotation context: the output is aggregate per-geohash-cell data (not listings), and thin cells are suppressed. It stops short of richer operational detail (rate limits, auth), but the suppression and aggregation notes are real value.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.