# Developer Configuration Layer

#### **Overview**

To make 402Gate developer-friendly, it includes a **configuration SDK** and **endpoint templates** that make any HTTP service instantly monetizable.

#### **Features**

* Simple middleware for Node.js / Next.js / Express.
* Built-in helpers to attach pricing logic per endpoint.
* Automatic generation of 402 responses and verification flow.
* TypeScript support for strict typing.

#### **Example Implementation**

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

app.use("/api/premium", create402Middleware({
  price: 0.001,
  token: "402G",
  recipient: "MERCHANT_PUBKEY",
  verifyOnChain: true
}));
```

#### **SDK Components**

* `create402Middleware()` — wrap protected endpoints.
* `verifyPayment()` — validate tx proof.
* `fetchWith402()` — client-side auto-retry for 402 responses.

#### **Developer Experience**

With the SDK, any developer can turn their REST API into a **Web3-native pay-per-use service** in minutes  without building a smart contract or handling complex crypto logic.


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