Quick Start

Step 1: Install the SDK

The 402Gate SDK makes integration with Solana seamless.

npm install @402gate/sdk

Or using Yarn:

yarn add @402gate/sdk

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Step 2: Import and Initialize

Use the SDK in your app (Node.js, Next.js, or Express).

import { create402Middleware } from "@402gate/sdk";

const middleware = create402Middleware({
  price: 0.001,
  token: "402G",
  recipient: "MERCHANT_PUBKEY",
  verifyOnChain: true
});

Attach it to your API route or service:

app.use("/api/premium", middleware);

This automatically:

• Detects unpaid requests and responds with HTTP 402 Payment Required.

• Verifies on-chain proof of payment.

• Grants access once valid.

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Step 3: Handle Client Payment

On the frontend or AI client side:

import { fetchWith402 } from "@402gate/sdk/client";

const response = await fetchWith402("https://api.402gate.app/premium", {
  wallet: userWallet,
  tokens: ["402G", "USDC", "SOL"]
});

If the endpoint responds with HTTP 402, the SDK will automatically:

• Parse the payment metadata (amount, token, requestId).

• Prompt user/agent to sign the transaction.

• Retry the request after payment is confirmed.