Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond them: pricing ($0.01/call, 10 free/day, x402 payment-required result), freshness (rebuilt every 6 hours), shrinkage behavior on thin samples, and error semantics (isError on invalid input or upstream failure, uncharged). This is unusually rich disclosure for a read-only tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.