Client Integration

Make T402 payments from your application.

TypeScript (Fetch)

The easiest way to integrate T402 is with the fetch wrapper:

import { t402Client, wrapFetchWithPayment } from '@t402/fetch'
import { registerExactEvmScheme } from '@t402/evm/exact/client'
import { privateKeyToAccount } from 'viem/accounts'
 
// 1. Create client
const client = new t402Client()
 
// 2. Register payment schemes
registerExactEvmScheme(client, {
  signer: privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`)
})
 
// 3. Wrap fetch
const fetchWithPayment = wrapFetchWithPayment(fetch, client)
 
// 4. Make requests - payments handled automatically!
const response = await fetchWithPayment('https://api.example.com/premium')
const data = await response.json()

Multi-Network Client

Support multiple blockchain networks:

import { t402Client, wrapFetchWithPayment } from '@t402/fetch'
import { registerExactEvmScheme } from '@t402/evm/exact/client'
import { registerExactTonClientScheme } from '@t402/ton'
import { registerExactTronClientScheme } from '@t402/tron'
 
const client = new t402Client()
 
// Register EVM (Ethereum, Base, Arbitrum, etc.)
registerExactEvmScheme(client, {
  signer: evmSigner
})
 
// Register TON
registerExactTonClientScheme(client, {
  signer: tonSigner,
  getJettonWalletAddress: async (owner, master) => {
    // Return the Jetton wallet address
    return jettonWalletAddress
  }
})
 
// Register TRON
registerExactTronClientScheme(client, {
  signer: tronSigner
})
 
// Now the client can pay on any supported network
const fetchWithPayment = wrapFetchWithPayment(fetch, client)

Axios Integration

import axios from 'axios'
import { t402AxiosInterceptor } from '@t402/axios'
import { registerExactEvmScheme } from '@t402/evm/exact/client'
 
const client = new t402Client()
registerExactEvmScheme(client, { signer })
 
// Add interceptor to axios instance
const api = axios.create({ baseURL: 'https://api.example.com' })
t402AxiosInterceptor(api, client)
 
// Make requests
const response = await api.get('/premium')

With Tether WDK

Use Tether WDK for wallet management:

import { WDK } from '@tetherto/wdk'
import { createWdkSigner } from '@t402/wdk'
 
// Initialize WDK
const wdk = new WDK({ /* config */ })
const account = await wdk.createAccount()
 
// Create signer from WDK account
const signer = createWdkSigner(account)
 
// Use with T402 client
const client = new t402Client()
registerExactEvmScheme(client, { signer })

Python Client

import httpx
from t402.client import T402Client
from t402.evm import create_evm_signer
 
# Create client
client = T402Client()
 
# Register EVM signer
signer = create_evm_signer(private_key="0x...")
client.register("eip155:8453", signer)
 
# Make request
async with httpx.AsyncClient() as http:
    response = await client.fetch(
        http,
        "https://api.example.com/premium"
    )
    data = response.json()

Go Client

package main
 
import (
    "fmt"
    t402 "github.com/t402-io/t402/go"
    "github.com/t402-io/t402/go/mechanisms/evm/exact/client"
)
 
func main() {
    // Create client
    c := t402.NewClient()
 
    // Register EVM scheme
    evmScheme := client.NewExactEvmScheme(privateKey)
    c.Register("eip155:8453", evmScheme)
 
    // Make request
    resp, err := c.Fetch("https://api.example.com/premium")
    if err != nil {
        panic(err)
    }
    fmt.Println(resp.Body)
}

Payment Preferences

Configure network preferences:

const client = new t402Client({
  // Prefer these networks (in order)
  preferredNetworks: ['eip155:8453', 'eip155:42161', 'eip155:1'],
 
  // Maximum amount willing to pay
  maxAmount: '10000000', // 10 USDT
 
  // Callback on payment
  onPayment: (payment) => {
    console.log(`Paid ${payment.amount} on ${payment.network}`)
  }
})

Error Handling

import { T402Error, PaymentRequiredError, PaymentFailedError } from '@t402/core'
 
try {
  const response = await fetchWithPayment('https://api.example.com/premium')
} catch (error) {
  if (error instanceof PaymentRequiredError) {
    console.log('Payment required:', error.requirements)
  } else if (error instanceof PaymentFailedError) {
    console.log('Payment failed:', error.reason)
  } else if (error instanceof T402Error) {
    console.log('T402 error:', error.message)
  }
}

Balance Checking

Check balances before making requests:

import { getBalance } from '@t402/evm'
 
// Check USDT0 balance on Base
const balance = await getBalance({
  address: '0x...',
  network: 'eip155:8453',
  token: 'USDT0'
})
 
console.log(`Balance: ${balance.formatted} USDT0`)

Server Integration