Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden, and it does disclose genuinely useful data-handling behavior: group separators and currency symbols are normalized, and non-numeric rows are excluded but still counted. It stops short of stating whether the call is read-only, what the response looks like, or how errors (missing/non-numeric column) surface.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.