Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false. The description adds a key behavioral detail beyond that: it does not register a visit, which is not captured by the annotations. This extra context is valuable for the agent to understand side effects (or lack thereof) and aligns with the idempotent nature.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.