Develop with Atum SDK

npm install @atumlabs/x402-atum-escrow @x402/core @x402/express

import { paymentMiddleware } from "@x402/express";
import { x402ResourceServer, HTTPFacilitatorClient } from "@x402/core/server";
import { registerAtumEscrowScheme, type AtumEscrowServerConfig } from "@atumlabs/x402-atum-escrow/server";

const config: AtumEscrowServerConfig = {
  // Where you receive: chain, token, and address.
  destination: { network: "eip155:42161", asset: "0x…USDC", address: "0x…merchant" },
  // Exact amount you receive, in atomic units of the destination token.
  fulfillmentAmount: "10000000",
  // Markup over fulfillmentAmount to derive each source cap, in basis points (300 = 3%).
  markupBps: 300,
  fulfillmentProxy: "0x…proxy",
  reserver: "0x…reserver",
  releaser: "0x…releaser",
  fulfillmentVerifierEndpoint: "https://…verifier",
  quoteDeadlineSeconds: 20,
  fulfillmentDeadlineSeconds: 300,
  // The source chains you accept, keyed by CAIP-2 network.
  sources: {
    "eip155:8453": { asset: "0x…baseUSDC", escrow: "0x…baseEscrow" },
    "eip155:42161": { asset: "0x…arbUSDC", escrow: "0x…arbEscrow" },
  },
};

const facilitatorClient = new HTTPFacilitatorClient({ url: process.env.FACILITATOR_URL! });
const server = registerAtumEscrowScheme(new x402ResourceServer(facilitatorClient), config);

// One accepts[] entry per source option, from the same config.
const accepts = Object.entries(config.sources).map(([network, source]) => ({
  scheme: "atum-escrow",
  network,
  payTo: source.escrow, // funds lock in the settlement vault, not with you
  price: "$0.10", // required by the route type, but ignored: the amount is fulfillmentAmount + markup
  maxTimeoutSeconds: 60,
}));

// Gate any route — an API endpoint, an MCP tool handler, whatever your
// agent-facing platform exposes.
app.use(paymentMiddleware({ "GET /paid": { accepts } }, server));