Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true), so the bar is lower. The description adds a genuinely non-obvious behavioral note — any result type may be empty for a query — which warns the agent about partial/empty responses. It does not cover pagination or result ordering, so not a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.