Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds genuine behavioral context beyond that: missing values stay unknown and insufficient observations cannot establish a winner, warning the agent against over-interpreting sparse results.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.