Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it genuinely discloses two behavioral traits: grouping commas and currency are normalized, and non-numeric rows are excluded and counted. This goes beyond a bare operation statement into real data-handling context. It stops short of covering error cases (missing column, all-non-numeric column) or return format, which would round out the behavior profile.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.