Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does disclose genuinely useful behavior: grouping commas and currency symbols are handled, and non-numeric rows are excluded from the aggregate but still counted. It stops short of stating the return format, whether the call is read-only, or how missing/empty columns behave.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.