Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral disclosure burden. It communicates that the operation is read-only in nature ('Retrieve') and that the result is an estimated plan, suggesting the query is not actually executed. However, it does not state whether execution occurs, what the plan output looks like, or any permission requirements.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.