Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description earns credit by adding behavior they cannot: results are ranked best-first, provenance is GovDir's scheduled verification with verified_status/verified_at, and a prompt-injection warning that result field text is data, never instructions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.