Using Non-USDC Tokens with x402

While USDC is commonly used with x402, the protocol supports any ERC-20 token. Configure your facilitator and middleware to accept multiple payment tokens.

Prerequisites

Understanding of ERC-20 tokens
Basic knowledge of x402 protocol
A SKALE Chain endpoint
Node.js and npm installed

Overview

x402 is token-agnostic and works with any ERC-20 compatible token. You can:

Accept multiple payment tokens
Allow users to choose their preferred token
Configure different prices for different tokens
Handle different token decimals

Multiple Payment Options in Middleware

Configure your middleware to accept multiple tokens:

import { createMiddleware } from "@faremeter/middleware/express";

const paywalled = await createMiddleware({
  facilitatorURL: "https://facilitator.dirtroad.dev",
  accepts: [
    [
      {
        scheme: "exact",
        network: "skale-base-sepolia",
        asset: "0x2e08028E3C4c2356572E096d8EF835cD5C6030bD",
        maxAmountRequired: "1.5",
        description: "SKALE USDC payment",
      },
      {
        scheme: "exact",
        network: "skale-base-sepolia",
        asset: "0x3ca0a49f511c2c89c4dcbbf1731120d8919050bf",
        maxAmountRequired: "1.5",
        description: "SKALE USDT payment",
      },
      {
        scheme: "exact",
        network: "skale-base-sepolia",
        asset: "0xf94056bd7f6965db3757e1b145f200b7346b4fc0",
        maxAmountRequired: "0.001",
        description: "SKALE WETH payment",
      },
    ],
  ],
});

Facilitator Configuration

Configure your facilitator to handle multiple tokens:

import { createFacilitator } from '@faremeter/facilitator';
import { createPaymentHandler } from '@faremeter/payment-evm';

const usdcHandler = createPaymentHandler({
  network: 'skale-base-sepolia',
  asset: '0x2e08028E3C4c2356572E096d8EF835cD5C6030bD',
  rpcUrl: 'YOUR_SKALE_RPC_URL',
});

const usdtHandler = createPaymentHandler({
  network: 'skale-base-sepolia',
  asset: '0x3ca0a49f511c2c89c4dcbbf1731120d8919050bf',
  rpcUrl: 'YOUR_SKALE_RPC_URL',
});

const facilitator = createFacilitator({
  network: 'skale-base-sepolia',
  paymentHandlers: [
    {
      scheme: 'exact',
      network: 'skale-base-sepolia',
      asset: '0x2e08028E3C4c2356572E096d8EF835cD5C6030bD',
      handler: usdcHandler,
    },
    {
      scheme: 'exact',
      network: 'skale-base-sepolia',
      asset: '0x3ca0a49f511c2c89c4dcbbf1731120d8919050bf',
      handler: usdtHandler,
    },
  ],
});

Token Selection

Allow clients to choose their payment token:

async function accessResource(url: string, preferredToken?: string) {
  const response = await fetch(url);
  
  if (response.status === 402) {
    const paymentInfo = await response.json();
    
    let selectedOption = paymentInfo.accepts[0];
    
    if (preferredToken) {
      const matchingOption = paymentInfo.accepts.find(
        (option) => option.asset?.toLowerCase() === preferredToken.toLowerCase()
      );
      if (matchingOption) {
        selectedOption = matchingOption;
      }
    }
    
    const payment = await x402Client.createPayment({
      ...selectedOption,
      resource: url,
    });
    
    await x402Client.settle(payment);
    
    const retryResponse = await fetch(url, {
      headers: {
        'X-PAYMENT': JSON.stringify(payment),
      },
    });
    
    return await retryResponse.json();
  }
  
  return await response.json();
}

Price Conversion

Handle different token prices:

const tokenPrices = {
  '0x2e08028E3C4c2356572E096d8EF835cD5C6030bD': 1.0,  // USDC - Base price
  '0x3ca0a49f511c2c89c4dcbbf1731120d8919050bf': 1.0,  // USDT - Same as USDC
  '0xf94056bd7f6965db3757e1b145f200b7346b4fc0': 3000.0, // WETH - ETH price in USD
};

function calculateAmount(tokenAddress: string, usdAmount: number): string {
  const price = tokenPrices[tokenAddress.toLowerCase()];
  const tokenAmount = usdAmount / price;
  return tokenAmount.toFixed(6);
}

// Use in middleware accepts
const accepts = [
  {
    scheme: 'exact',
    network: 'skale-base-sepolia',
    asset: '0x2e08028E3C4c2356572E096d8EF835cD5C6030bD',
    maxAmountRequired: '1.5',
  },
  {
    scheme: 'exact',
    network: 'skale-base-sepolia',
    asset: '0xf94056bd7f6965db3757e1b145f200b7346b4fc0',
    maxAmountRequired: calculateAmount('0xf94056bd7f6965db3757e1b145f200b7346b4fc0', 1.5),
  },
];

Handling Different Decimals

const accepts = [
  {
    scheme: 'exact',
    network: 'skale-base-sepolia',
    asset: '0x2e08028E3C4c2356572E096d8EF835cD5C6030bD',
    maxAmountRequired: ethers.parseUnits('1.5', 6).toString(),
  },
  {
    scheme: 'exact',
    network: 'skale-base-sepolia',
    asset: '0xf94056bd7f6965db3757e1b145f200b7346b4fc0',
    maxAmountRequired: ethers.parseUnits('0.001', 18).toString(),
  },
];

Common Tokens on SKALE Base Sepolia

Popular tokens available on SKALE Base Sepolia:

USDC: 0x2e08028E3C4c2356572E096d8EF835cD5C6030bD - Stablecoin, 6 decimals
USDT: 0x3ca0a49f511c2c89c4dcbbf1731120d8919050bf - Stablecoin, 6 decimals
WBTC: 0x4512eacd4186b025186e1cf6cc0d89497c530e87 - Wrapped Bitcoin, 8 decimals
ETH (ERC-20): 0xD2Aaa00700000000000000000000000000000000 - Native ETH as ERC-20
WETH: 0xf94056bd7f6965db3757e1b145f200b7346b4fc0 - Wrapped ETH, 18 decimals
SKL: 0xaf2e0ff5b5f51553fdb34ce7f04a6c3201cee57b - SKALE Token, 18 decimals
AxiosUSD: 0x61a26022927096f444994dA1e53F0FD9487EAfcf - Test stablecoin

Deployment

Smart Contracts

Privacy

x402

MPP

Facilitators

AI Agents

Native Features

Prerequisites

Overview

Multiple Payment Options in Middleware

Facilitator Configuration

Token Selection

Price Conversion

Handling Different Decimals

Common Tokens on SKALE Base Sepolia

Resources

​Prerequisites

​Overview

​Multiple Payment Options in Middleware

​Facilitator Configuration

​Token Selection

​Price Conversion

​Handling Different Decimals

​Common Tokens on SKALE Base Sepolia

​Resources

Prerequisites

Overview

Multiple Payment Options in Middleware

Facilitator Configuration

Token Selection

Price Conversion

Handling Different Decimals

Common Tokens on SKALE Base Sepolia

Resources