Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden and does a good job: it discloses that grouping commas and currency symbols are handled, and that non-numeric rows are excluded and counted. This is genuinely useful beyond the title and schema. It does not mention failure modes or return shape, but the core quirks are surfaced.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.