Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover the read-only and open-world profile, and the description adds material behavior beyond them: the call is paid ($0.003 USDC on Base via x402), which is critical for an agent to know before invoking. It also signals coverage limits (requires a DEX pool), though it omits rate limits or failure behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.