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 real data-handling behavior: grouping commas and currency symbols are parsed, and non-numeric rows are excluded and counted. However, it says nothing about permission requirements, failure modes (e.g. a column with zero numeric values), or the shape of the returned result.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.