x402-agent-example

# Pay an API with x402 — in about ten lines

[x402](https://x402.org) is HTTP 402 put to work: a server answers `402 Payment Required`
with the exact price, the client signs a stablecoin payment and repeats the same request.
No account, no API key, no invoice.

These examples call [DexL Agents](https://agents.dexl.io), an x402 gateway
(chat models, speech, web search and crawl, on-chain reads, FX rates, NLP tools).
Everything here works against any x402 server — only the URL changes.

## 1. Free: no wallet at all

```bash
npm install
npm run free
```

`free.mjs` does two things:

- calls the **free tier** (`model: "dexl-free"`) — no payment header, no wallet, no account;
- asks what a **paid** call would cost by sending it *without* payment and reading the 402.

Real output:

```
free answer: HTTP 402 (Payment Required) is a non-standardized status code reserved for future use...
web-search costs 0.01 USDC on eip155:8453 (HTTP 402)
```

## 2. Paid: one call, one signature

```bash
PRIVATE_KEY=0x... npm run paid
```

The payment is these three lines; after them it is ordinary `fetch`:

```js
const signer = toClientEvmSigner(wallet);
const client = new x402Client().register('eip155:8453', new ExactEvmScheme(signer));
const fetchWithPay = wrapFetchWithPayment(fetch, client);
```

Your key stays on your machine — the server only ever sees a signed payment.
Settles in USDC on Base, Polygon, Arbitrum or Solana. **Error responses are not charged.**

> The free example above was run as-is. The paid one needs your own funded wallet,
> so run it yourself with a small balance; it uses the same client our own service uses.

## 3. Connect an MCP client

Remote (free tools only — a remote server holds no wallet of yours):

```
https://agents.dexl.io/mcp
```

Local, with paid tools, because the wallet stays on your machine:

```json
{
  "mcpServers": {
    "dexl": {
      "command": "npx",
      "args": ["-y", "dexl-agents", "mcp"],
      "env": { "DEXL_BASE_URL": "https://agents.dexl.io", "DEXL_PRIVATE_KEY": "<optional>" }
    }
  }
}
```

## What you can call

`GET /v1/tools` lists every tool with its price and schema.
Machine-readable: [`/llms.txt`](https://agents.dexl.io/llms.txt) ·
[`/openapi.json`](https://agents.dexl.io/openapi.json) ·
[`/.well-known/x402`](https://agents.dexl.io/.well-known/x402) ·
[`/.well-known/mcp`](https://agents.dexl.io/.well-known/mcp)

MIT licensed. Issues and pull requests welcome.