Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered without the description. The description adds only the scoping fact that the index belongs to one project; it says nothing about pagination, result ordering, or whether page content is included. With annotations carrying the safety burden, this is an adequate but thin contribution.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.