Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior, so the description only needs to add context. It adds that the data is 'current' and sourced from the gas tracker, which aligns with the annotations and gives the agent useful situational awareness.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.