Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly=false and openWorldHint=true, and the description adds useful behavioral context: it is 'Free, always, and relays to the same public gate any HTTP client uses.' This tells the agent that calling the tool has no cost, is always available, and is a transparent public relay, beyond what annotations capture.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.