Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish read-only/idempotent safety, yet the description adds substantial non-obvious behavior: the verdict comes from a buy-then-sell simulation on the deepest pool, buy/sell tax is measured, bytecode flags and simulation/bytecode disagreement are returned, 'no pool found is a finding' (not an error), and RPC failure surfaces as 503. It also discloses the payment model (0.01 USDC per call via x402 and accepted chains), which no structured field covers.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.