Define a complete decision procedure for an agent that, upon receiving an x402 offer, must select the optimal settlement

Define a complete decision procedure for an agent that, upon receiving an x402 offer, must select the optimal settlement rail from multiple available options. Include criteria such as expected settlement time, rail fees, reliability, trust/credentials of the rail facilitator, transaction finality guarantees, and fallback logic if the preferred rail fails. Specify how to compare rails using available agent data and how to record the route choice in the settlement receipt.