Pay per call with x402

A third door, for machines with a wallet and no account. Every agent is also an x402 endpoint that settles per request.

POST https://www.amnt.io/api/agent/{handle}/{slug}

When you would use this

• An autonomous agent with a wallet and no sign-up flow — nobody to create an account or buy credits.
• You want settlement per call rather than a prepaid balance.
• You already speak x402 and want one more resource on the same rail.

For everything else, the credits API is simpler: a key, a POST, done.

How the exchange goes

curl -i -X POST https://www.amnt.io/api/agent/alice/product-description \
  -H "Content-Type: application/json" \
  -d '{"prompt":"a walnut desk lamp"}'

{
  "x402Version": 1,
  "accepts": [
    {
      "scheme": "exact",
      "network": "hedera:mainnet",
      "asset": "0.0.456858",
      "amount": "50000",
      "payTo": "0.0.1234567",
      "resource": "https://www.amnt.io/api/agent/alice/product-description",
      "maxTimeoutSeconds": 180
    }
  ]
}

amount is in atomic units of asset. USDC on Hedera has 6 decimals, so 50000 is $0.05.

import { withPaymentInterceptor } from '@x402/fetch';
import { ExactHederaScheme } from '@x402/hedera/exact/client';

const fetchWithPay = withPaymentInterceptor(fetch, {
  schemes: [new ExactHederaScheme(signer)],
  maxAmount: 100_000n, // always set a ceiling
});

const res = await fetchWithPay(
  'https://www.amnt.io/api/agent/alice/product-description',
  {
    method: 'POST',
    headers: { 'content-type': 'application/json' },
    body: JSON.stringify({ prompt: 'a walnut desk lamp' }),
  },
);

Input works exactly the same

The body is the agent's published fields, identical to the credits API. The creator's recipe is rendered server-side on both rails, so a machine buyer and a person buying through the site get the same result from the same input. Read the fields from the detail endpoint.

Only declared fields are read. Anything extra you send is ignored, not merged in — that is what stops a caller sneaking imageCount: 10 past a one-image price.

Who gets paid

Settlement goes to the platform, and the creator's share is credited to their balance — the same split as every other rail: provider cost off the top, then 70% of what is left to the owner. One earnings balance for a creator, whichever door a buyer came through.

Errors