x402-client

@dexterai/x402 Client SDK

Use the V6 one-shot client to probe an endpoint once, detect its x402 version, sign an accepted USDC payment, and send the paid request.

This is an independent application-owned executor. It is not the OpenDexter MCP runtime, does not inherit an OpenDexter OAuth bearer or governed grant, and must never become a fallback for a blocked OpenDexter operation. Keep private keys out of prompts, logs, tool output, and source control.

Install the tested V6 pair

Use Node 22 or newer and install the exact Vault peer with the SDK:

npm install @dexterai/[email protected] @dexterai/[email protected]

Canonical one-shot payment

import {
  createEvmKeypairWallet,
  createKeypairWallet,
  payAndFetch,
} from '@dexterai/x402/client';

const wallets = {
  solana: await createKeypairWallet(process.env.SOLANA_PRIVATE_KEY!),
  evm: await createEvmKeypairWallet(process.env.EVM_PRIVATE_KEY!),
};

const result = await payAndFetch(
  'https://api.example.com/paid/data',
  { method: 'GET' },
  wallets,
  {
    maxAmountAtomic: '100000', // at most $0.10 USDC for this call
    solanaRpcUrl: process.env.SOLANA_RPC_URL,
  },
);

if (!result.ok) {
  if (result.reason === 'payment_unconfirmed') {
    throw new Error(`Payment may have settled; reconcile before retrying: ${result.detail}`);
  }
  throw new Error(`Payment failed before delivery: ${result.reason}: ${result.detail ?? ''}`);
}

if (!result.response) {
  // paid:true with no response means settlement was confirmed but the
  // merchant did not answer. Never turn this into an automatic second pay.
  throw new Error('Payment settled, but the merchant returned no response');
}

const data = await result.response.json();
console.log(data);

payAndFetch handles x402 V1 and V2. It returns a discriminated PayResult instead of throwing for expected payment failures:

• ok: true, paid: false: the endpoint returned without requiring payment.
• ok: true, paid: true: payment settled; response can still be absent if the merchant never answered after settlement.
• ok: false, reason: 'timeout': no authorization was sent; a retry can be safe after reviewing the request.
• ok: false, reason: 'payment_unconfirmed': authorization was sent and may have settled. Do not blindly retry.