Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false. The description adds that the guide is 'structured public', which is useful context about data access and format. That additional context justifies a 3, but the heavy lifting is done by annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.