Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Beyond the idempotentHint annotation, the description adds meaningful behavioral context: setting public=true causes publication, creates a share page, and provides a public GLB URL for download. This is valuable side-effect information that the annotations alone do not convey.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.