Quickstart

MERIDIAN_API_KEY=pk_test_...

// Example: Base mainnet. Swap in any supported network's values.
const NETWORK = {
  id: "base",
  chainId: 8453,
  token: "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", // USDC
  tokenName: "USD Coin", // EIP-712 domain name of the token
  tokenVersion: "2",     // EIP-712 domain version of the token
  facilitator: "0x8E7769D440b3460b92159Dd9C6D17302b036e2d6",
};

const paymentRequirements = {
  scheme: "exact",
  network: NETWORK.id,
  asset: NETWORK.token,
  payTo: NETWORK.facilitator,
  maxAmountRequired: "10000", // $0.01 in USDC base units (6 decimals)
  resource: "https://your-api.example.com/api/premium",
  description: "Access to premium content",
  mimeType: "application/json",
  maxTimeoutSeconds: 300,
  extra: { name: NETWORK.tokenName, version: NETWORK.tokenVersion },
};

return Response.json(
  { x402Version: 1, accepts: [paymentRequirements] },
  { status: 402 },
);

import { bytesToHex } from "viem";

const now = BigInt(Math.floor(Date.now() / 1000));
const authorization = {
  from: account.address,
  to: paymentRequirements.payTo as `0x${string}`,
  value: BigInt(paymentRequirements.maxAmountRequired),
  validAfter: 0n,
  validBefore: now + BigInt(paymentRequirements.maxTimeoutSeconds),
  nonce: bytesToHex(crypto.getRandomValues(new Uint8Array(32))),
};

const signature = await walletClient.signTypedData({
  account,
  domain: {
    name: paymentRequirements.extra.name,
    version: paymentRequirements.extra.version,
    chainId: NETWORK.chainId,
    verifyingContract: paymentRequirements.asset as `0x${string}`,
  },
  types: {
    TransferWithAuthorization: [
      { name: "from", type: "address" },
      { name: "to", type: "address" },
      { name: "value", type: "uint256" },
      { name: "validAfter", type: "uint256" },
      { name: "validBefore", type: "uint256" },
      { name: "nonce", type: "bytes32" },
    ],
  },
  primaryType: "TransferWithAuthorization",
  message: authorization,
});

const paymentPayload = {
  x402Version: 1,
  scheme: "exact",
  network: paymentRequirements.network,
  payload: {
    signature,
    authorization: {
      from: authorization.from,
      to: authorization.to,
      value: authorization.value.toString(),
      validAfter: authorization.validAfter.toString(),
      validBefore: authorization.validBefore.toString(),
      nonce: authorization.nonce,
    },
  },
};

if (paymentPayload.network !== paymentRequirements.network) {
  throw new Error("Payment network does not match the server requirement");
}

if (
  paymentPayload.payload.authorization.to.toLowerCase() !==
  paymentRequirements.payTo.toLowerCase()
) {
  throw new Error("Payment must authorize the Meridian facilitator");
}

if (
  paymentPayload.payload.authorization.value !==
  paymentRequirements.maxAmountRequired
) {
  throw new Error("Payment amount does not match the server price");
}

const response = await fetch("https://api.mrdn.finance/v1/settle", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.MERIDIAN_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({ paymentPayload, paymentRequirements }),
});

const result = await response.json();
if (!response.ok || !result.success) {
  throw new Error(result.errorReason ?? "Settlement failed");
}