Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so safety is covered; the description still adds real behavioral context the annotations cannot carry, notably the A-grade-only scope, the caveat that absence does not imply untrustworthiness, the 100-row ceiling, and the disclaimer that no ranking or endorsement is implied. That is a meaningful addition beyond structured fields.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.