Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, but it does disclose real behavioral traits: grouping commas and currency symbols are handled, and non-numeric rows are excluded and counted. It leaves the return format, the handling of an all-non-numeric or nonexistent column, and the destination of the 'counted' non-numeric rows unexplained.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.