Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered; the description goes further by disclosing that columns are auto-detected, headers aligned, and missing keys rendered as empty cells — defaults an agent could not infer from the schema. No detail on how nested or non-object values are handled, but for a pure transform that is minor.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.