Make Payments

This guide shows how to make x402 payments from the buyer’s perspective. Use the SDK to handle payment flows, interact with paywalled resources, and process 402 Payment Required responses.

Prerequisites

Node.js and npm installed
A SKALE Chain endpoint
Understanding of x402 protocol
Familiarity with TypeScript
A wallet with funds (USDC or supported token)

Overview

When accessing a paywalled resource, the flow is:

Make a request to the protected endpoint
Receive a 402 Payment Required response with payment requirements
Create and sign a payment authorization
Retry the request with the payment signature header

Environment Setup

Create a .env file with the following variables:

# Your wallet private key (never commit this!)
PRIVATE_KEY=0xYourPrivateKey

# USDC token contract on SKALE
PAYMENT_TOKEN_ADDRESS=0x2e08028E3C4c2356572E096d8EF835cD5C6030bD
PAYMENT_TOKEN_NAME="Bridged USDC (SKALE Bridge)"

Implementation

Coinbase SDK
Faremeter SDK

Step 1: Install Dependencies

npm install @x402/core @x402/evm viem dotenv

Step 2: Define Your Chain

Create a chain configuration for SKALE:

import { defineChain } from "viem";

export const skaleChain = defineChain({
    id: 324705682,
    name: "SKALE Base Sepolia",
    nativeCurrency: { decimals: 18, name: "Credits", symbol: "CREDIT" },
    rpcUrls: {
        default: { http: ["https://base-sepolia-testnet.skalenodes.com/v1/base-testnet"] },
    },
});

Step 3: Create the Payment Client

import { x402Client, x402HTTPClient } from "@x402/core/client";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";
import "dotenv/config";

const account = privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`);

// Create the x402 client with EVM scheme
const evmScheme = new ExactEvmScheme(account);
const coreClient = new x402Client().register("eip155:*", evmScheme);
const httpClient = new x402HTTPClient(coreClient);

Step 4: Access Paywalled Resources

async function accessResource(url: string): Promise<unknown> {
    // Make initial request
    const response = await fetch(url, {
        method: "GET",
        headers: { "Content-Type": "application/json" },
    });

    // If no payment required, return data
    if (response.status !== 402) {
        return response.json();
    }

    // Get payment requirements from response
    const responseBody = await response.json();
    const paymentRequired = httpClient.getPaymentRequiredResponse(
        (name: string) => response.headers.get(name),
        responseBody
    );

    // Create payment payload (signs the authorization)
    const paymentPayload = await httpClient.createPaymentPayload(paymentRequired);

    // Get payment headers to send with retry request
    const paymentHeaders = httpClient.encodePaymentSignatureHeader(paymentPayload);

    // Retry request with payment
    const paidResponse = await fetch(url, {
        method: "GET",
        headers: {
            "Content-Type": "application/json",
            ...paymentHeaders,
        },
    });

    if (!paidResponse.ok) {
        throw new Error(`Payment failed: ${paidResponse.status}`);
    }

    return paidResponse.json();
}

Complete Working Example

import { x402Client, x402HTTPClient } from "@x402/core/client";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";
import { createPublicClient, http, formatEther } from "viem";
import { defineChain } from "viem";
import "dotenv/config";

export const skaleChain = defineChain({
    id: 324705682,
    name: "SKALE Base Sepolia",
    nativeCurrency: { decimals: 18, name: "Credits", symbol: "CREDIT" },
    rpcUrls: {
        default: { http: ["https://base-sepolia-testnet.skalenodes.com/v1/base-testnet"] },
    },
});

async function main() {
    const privateKey = process.env.PRIVATE_KEY;
    if (!privateKey) {
        throw new Error("PRIVATE_KEY environment variable is required");
    }

    // Setup wallet
    const account = privateKeyToAccount(privateKey as `0x${string}`);
    console.log(`Wallet address: ${account.address}`);

    // Setup x402 client
    const evmScheme = new ExactEvmScheme(account);
    const coreClient = new x402Client().register("eip155:*", evmScheme);
    const httpClient = new x402HTTPClient(coreClient);

    // Access paywalled resource
    const url = "http://localhost:3000/premium/data";

    try {
        const response = await fetch(url, {
            method: "GET",
            headers: { "Content-Type": "application/json" },
        });

        if (response.status === 402) {
            console.log("Payment required, processing...");

            const responseBody = await response.json();
            const paymentRequired = httpClient.getPaymentRequiredResponse(
                (name: string) => response.headers.get(name),
                responseBody
            );

            const paymentPayload = await httpClient.createPaymentPayload(paymentRequired);
            const paymentHeaders = httpClient.encodePaymentSignatureHeader(paymentPayload);

            const paidResponse = await fetch(url, {
                method: "GET",
                headers: {
                    "Content-Type": "application/json",
                    ...paymentHeaders,
                },
            });

            const data = await paidResponse.json();
            console.log("Premium data:", data);
        } else {
            const data = await response.json();
            console.log("Data:", data);
        }
    } catch (error) {
        console.error("Error:", error);
    }
}

main();

Run the Client

npx tsx client.ts

Step 1: Install Dependencies

npm install @faremeter/fetch @faremeter/wallet-evm @faremeter/payment-evm viem dotenv

Step 2: Define Your Chain

Create a chain configuration for SKALE:

import { defineChain } from "viem";

export const skaleChain = defineChain({
    id: 324705682,
    name: "SKALE Base Sepolia",
    nativeCurrency: { decimals: 18, name: "Credits", symbol: "CREDIT" },
    rpcUrls: {
        default: { http: ["https://base-sepolia-testnet.skalenodes.com/v1/base-testnet"] },
    },
});

Step 3: Create the Payment-Enabled Fetch

The Faremeter SDK wraps the native fetch function to automatically handle 402 responses:

import { createLocalWallet } from "@faremeter/wallet-evm";
import { createPaymentHandler } from "@faremeter/payment-evm/exact";
import { wrap as wrapFetch } from "@faremeter/fetch";
import "dotenv/config";

const wallet = await createLocalWallet(skaleChain, process.env.PRIVATE_KEY!);

const fetchWithPayment = wrapFetch(fetch, {
    handlers: [
        createPaymentHandler(wallet, {
            asset: {
                address: process.env.PAYMENT_TOKEN_ADDRESS as `0x${string}`,
                contractName: process.env.PAYMENT_TOKEN_NAME || "Bridged USDC (SKALE Bridge)",
                forwarderName: process.env.PAYMENT_TOKEN_NAME || "Bridged USDC (SKALE Bridge)",
                forwarderVersion: "1",
            },
        }),
    ],
});

Step 4: Access Paywalled Resources

// The wrapped fetch automatically handles 402 responses
const response = await fetchWithPayment("http://localhost:3000/premium/data", {
    method: "GET",
    headers: { "Content-Type": "application/json" },
});

const data = await response.json();
console.log("Premium data:", data);

Complete Working Example

import { createLocalWallet } from "@faremeter/wallet-evm";
import { createPaymentHandler } from "@faremeter/payment-evm/exact";
import { wrap as wrapFetch } from "@faremeter/fetch";
import { createPublicClient, http, formatEther, defineChain } from "viem";
import "dotenv/config";

export const skaleChain = defineChain({
    id: 324705682,
    name: "SKALE Base Sepolia",
    nativeCurrency: { decimals: 18, name: "Credits", symbol: "CREDIT" },
    rpcUrls: {
        default: { http: ["https://base-sepolia-testnet.skalenodes.com/v1/base-testnet"] },
    },
});

async function main() {
    const privateKey = process.env.PRIVATE_KEY;
    if (!privateKey) {
        throw new Error("PRIVATE_KEY environment variable is required");
    }

    // Setup wallet
    const wallet = await createLocalWallet(skaleChain, privateKey);
    console.log(`Wallet address: ${wallet.account.address}`);

    // Setup payment-enabled fetch
    const assetAddress = process.env.PAYMENT_TOKEN_ADDRESS as `0x${string}`;
    const assetName = process.env.PAYMENT_TOKEN_NAME || "Bridged USDC (SKALE Bridge)";

    const fetchWithPayment = wrapFetch(fetch, {
        handlers: [
            createPaymentHandler(wallet, {
                asset: {
                    address: assetAddress,
                    contractName: assetName,
                    forwarderName: assetName,
                    forwarderVersion: "1",
                },
            }),
        ],
    });

    // Access paywalled resource - payment handled automatically!
    const url = "http://localhost:3000/premium/data";

    try {
        console.log(`Accessing ${url}...`);

        const response = await fetchWithPayment(url, {
            method: "GET",
            headers: { "Content-Type": "application/json" },
        });

        if (!response.ok) {
            throw new Error(`Request failed: ${response.status}`);
        }

        const data = await response.json();
        console.log("Premium data:", data);
    } catch (error) {
        console.error("Error:", error);
    }
}

main();

Run the Client

npx tsx client.ts

POST Requests with Body

The wrapped fetch works the same way for POST requests:

const response = await fetchWithPayment("http://localhost:3000/premium/analyze", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({ query: "analyze this data" }),
});

const result = await response.json();
console.log("Analysis result:", result);

Testing Your Client

Make sure you have a server running (see Accept Payments), then run your client:

npx tsx client.ts

The client will:

Make a request to the protected endpoint
Receive the 402 response with payment requirements
Sign a payment authorization using your wallet
Retry the request with the payment header
Receive the premium content

Deployment

Smart Contracts

Privacy

x402

MPP

Facilitators

AI Agents

Native Features

Prerequisites

Overview

Environment Setup

Implementation

Step 1: Install Dependencies

Step 2: Define Your Chain

Step 3: Create the Payment Client

Step 4: Access Paywalled Resources

Complete Working Example

Run the Client

Step 1: Install Dependencies

Step 2: Define Your Chain

Step 3: Create the Payment-Enabled Fetch

Step 4: Access Paywalled Resources

Complete Working Example

Run the Client

POST Requests with Body

Testing Your Client

Best Practices

Security Considerations

Resources

​Prerequisites

​Overview

​Environment Setup

​Implementation

​Step 1: Install Dependencies

​Step 2: Define Your Chain

​Step 3: Create the Payment Client

​Step 4: Access Paywalled Resources

​Complete Working Example

​Run the Client

​Step 1: Install Dependencies

​Step 2: Define Your Chain

​Step 3: Create the Payment-Enabled Fetch

​Step 4: Access Paywalled Resources

​Complete Working Example

​Run the Client

​POST Requests with Body

​Testing Your Client

​Best Practices

​Security Considerations

​Resources

Prerequisites

Overview

Environment Setup

Implementation

Step 1: Install Dependencies

Step 2: Define Your Chain

Step 3: Create the Payment Client

Step 4: Access Paywalled Resources

Complete Working Example

Run the Client

Step 1: Install Dependencies

Step 2: Define Your Chain

Step 3: Create the Payment-Enabled Fetch

Step 4: Access Paywalled Resources

Complete Working Example

Run the Client

POST Requests with Body

Testing Your Client

Best Practices

Security Considerations

Resources