# Buy SourceMint evidence with x402

Install `@x402/fetch`, `@x402/evm`, and `viem`, then create an x402 client with a Base wallet holding native USDC.

```js
import { x402Client, wrapFetchWithPayment } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const signer = privateKeyToAccount(process.env.EVM_PRIVATE_KEY);
const client = new x402Client();
registerExactEvmScheme(client, { signer });
const paidFetch = wrapFetchWithPayment(fetch, client);

const response = await paidFetch(
  "https://sourcemint-api.nap6281.chatgpt.site/api/audit-citations",
  {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify({
      answer: "Example Domain is maintained for illustrative examples.",
      urls: ["https://example.com"],
    }),
  },
);

console.log(await response.json());
```

Prices are declared in `/openapi.json` and in each endpoint's unsigned HTTP 402 challenge. Inspect those requirements before authorizing payments in high-value workflows.