Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations present, the description carries full disclosure and does meaningful work: it specifies the exact return contents (count, min, max, mean, median, sum), states that grouping commas and currency are handled, and discloses that non-numeric rows are excluded and counted. What remains unstated is the failure mode for an unknown or wholly non-numeric column and any permission requirements, which keeps it short of a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.