┌──────┐   ┌──────┐   ┌──────┐   ┌──────┐   ┌──────┐
  │ CALL │──▶│  402 │──▶│ PAY  │──▶│  TX  │──▶│  OK  │
  └──────┘   └──────┘   └──────┘   └──────┘   └──────┘
    01         02         03         04         05
              ~1.4s round-trip · 0.0001 USDC + gas

Quickstart

Pay a toll, run a call. Five steps, zero accounts. Examples use the forthcoming TOLL gateway URL — drop in your own x402-compatible endpoint today if you want to test the flow.

01 · Point an agent at the gateway

Any HTTP client works. The example uses pseudocode close to what an MCP-style agent loop looks like.

const TOLL_GATEWAY = "https://toll.computer/v1";

const agent = new Agent({
  wallet: yourBaseWallet,   // any EOA or smart wallet on Base
  toolPaymentLimit: 0.05,   // hard cap per call, USDC
});

02 · Make a call

The agent issues a normal HTTP POST to a registered tool. No API key, no session, no signup.

const res = await fetch(
  `${TOLL_GATEWAY}/tools/crypto.price`,
  {
    method: "POST",
    body: JSON.stringify({ ticker: "ETH" }),
  }
);

03 · Handle the 402

If the tool requires payment, the gateway returns HTTP 402 Payment Required with payment metadata in headers.

HTTP/1.1 402 Payment Required
X-Payment-Required: 0.0001 USDC
X-Payment-Address: 0x7a3...d22f
X-Payment-Chain:   base
X-Payment-Token:   USDC
X-Payment-Nonce:   01HXT7...K9

04 · Settle on Base

The agent's wallet signs a USDC transfer for the requested amount to the requested address on Base. Sub-second confirmation, fee under one cent.

const tx = await agent.wallet.transfer({
  token: "USDC",
  chain: "base",
  to: paymentHeader.address,
  amount: paymentHeader.amount,
  nonce: paymentHeader.nonce,
});

await tx.wait(); // ~600ms on Base

05 · Retry with the receipt

Re-send the original request with X-Payment-Receipt: <tx hash>. The gateway verifies the on-chain payment and returns the tool's response.

const final = await fetch(
  `${TOLL_GATEWAY}/tools/crypto.price`,
  {
    method: "POST",
    headers: { "X-Payment-Receipt": tx.hash },
    body: JSON.stringify({ ticker: "ETH" }),
  }
);

// → 200 OK
// { "ticker": "ETH", "price": 3847.21, "ts": 1763680842 }

The whole loop

agent ──▶ tool      (POST)
agent ◀── 402       (price, address, nonce)
agent ──▶ Base      (sign USDC tx)
Base  ◀── confirmed (block, hash)
agent ──▶ tool      (retry + receipt)
agent ◀── 200       (response)

total: ~1.4s · cost: 0.0001 USDC + ~0.0003 USDC gas

Next steps

• Read the x402 protocol spec we implement.
• See how $TOLL is used by tool operators and curators.
• Want to list a tool? Join the early-operator channel (see footer).