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 meaningful data-handling behavior: grouping commas and currency values are parsed, and non-numeric rows are excluded and counted. It does not, however, say whether the operation is read-only (implied), how errors surface for a non-existent or non-numeric column, or the shape of the returned values.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.