Quick Start

Integrate Cross402 into your application in three simple steps.

1. Install the SDK

Choose your preferred environment:

• Node.js: npm install @cross402/usdc
• Go: go get github.com/cross402/usdc-sdk-go

2. Get Your API Keys

Before initializing the client, you need to obtain your API key and secret key:

1. Visit https://agent.tech/dashboard
2. Sign in with your email
3. Click "Create Agent" to create a new agent
4. Generate your API key and secret key from the agent dashboard

Note: Each account can create up to 10 agents. For detailed instructions, see the Authentication documentation.

danger "Protect your keys"

Always store your API key and secret key in environment variables. Never hardcode them in source code or share them in any chat, AI assistant, or support channel. A leaked key can be used to initiate payments from your wallet, resulting in permanent fund loss.

3. Initialize the Client

Node.js / TypeScript

import { PayClient } from '@cross402/usdc';

const client = new PayClient({
  baseUrl: 'https://api-pay.agent.tech',
  auth: { apiKey: 'your-api-key', secretKey: 'your-secret-key' },
});

Go

import "github.com/cross402/usdc-sdk-go"

client, err := pay.NewClient(
    "https://api-pay.agent.tech",
    pay.WithBearerAuth(apiKey, secretKey),
)

4. Create an Intent

An "Intent" represents a payment request. You pick where the payer sends the stablecoin (payerChain) and where the merchant receives it (targetChain, optional — defaults to "base"). In this example the payer sends on Base and the merchant is paid on Ethereum.

const intent = await client.createIntent({
  email: "merchant@example.com",
  amount: "100.50",
  payerChain: "base",
  targetChain: "ethereum",
});

targetChain is optional. Omit it to keep v1 behaviour (settle on Base). If you pass it, the value must be a chain listed by GET /api/chains; otherwise the request is rejected with 400 invalid target_chain. Full matrix and per-chain caveats in Supported Chains.

5. Finalize Payment

Depending on your integration type, choose one of the following methods to complete the transaction:

Method A: Server-side (Automated)

Ideal for automated payouts or background tasks where the Agent wallet signs on behalf of the system.

• Action: Call the execute method.
• Code: await client.executeIntent(intentId);

Method B: Client-side (User-initiated)

Ideal for e-commerce checkouts where the actual user (payer) must sign with their own wallet (e.g., MetaMask).

1. Sign: The payer signs the X402 payment off-chain via their wallet.
2. Submit: Use the SDK to submit the settlement proof to our API.

• Code: await client.submitProof(intentId, settleProof);

Poll client.getIntent(intentId) until status === "TARGET_SETTLED" (success) or one of the terminal failure states (EXPIRED, VERIFICATION_FAILED, PARTIAL_SETTLEMENT). The full state machine is in Statuses.