Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations present, the description carries the behavioral burden and handles it well. It discloses that grouping commas and currency are parsed, and that non-numeric rows are excluded and counted. This gives the agent meaningful expectations beyond the tool's basic purpose, though it does not describe output structure or error behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.