x402 discovery

The discovery feed is Cryptonly’s public list of paid endpoints. AI agents and x402 directories read it to find APIs they can pay for. Listing is optional and free.

List an endpoint priced in the dashboard

Turn on List publicly when you add or edit an endpoint. The Status column of the Endpoints tab shows which endpoints are listed.

Open endpoints

Install @x402/extensions next to your @cryptonly/x402-* package too. It then adds the endpoint’s input and output to its 402 response, so agents know how to call it.

The Advanced fields describe the endpoint for agents:

Field	What it tells agents
Payment timeout	How long a signed payment stays valid. Sent as maxTimeoutSeconds.
Response type	The content type of the response, such as application/json.
Input JSON Schema	How to call the endpoint: query parameters for GET, HEAD and DELETE, the body for POST, PUT and PATCH.
Output JSON Schema	What the endpoint returns.

List an endpoint priced in code

Add the Bazaar extension to the route, on top of the setup from Prices in your code:

ExpressNestJSPython

import { bazaarResourceServerExtension, declareDiscoveryExtension } from '@x402/extensions/bazaar';

server.registerExtension(bazaarResourceServerExtension);

app.use(
  paymentMiddleware(
    {
      'GET /v1/quote/:symbol': {
        accepts: [
          { scheme: 'exact', price: '$0.005', network: 'eip155:8453', payTo: process.env.PAY_TO! },
        ],
        description: 'Token price quote',
        extensions: declareDiscoveryExtension({
          output: { example: { symbol: 'SOL', usd: 150.25 } },
        }),
      },
    },
    server,
  ),
);

import { declareDiscoveryExtension } from '@x402/extensions/bazaar';

@X402({
  accepts: { scheme: 'exact', price: '$0.005', network: 'eip155:8453', payTo: process.env.PAY_TO! },
  description: 'Token price quote',
  extensions: declareDiscoveryExtension({
    output: { example: { symbol: 'SOL', usd: 150.25 } },
  }),
})
@Get('quote/:symbol')
quote(@Param('symbol') symbol: string) {
  return { symbol, usd: 150.25 };
}

@X402() registers the Bazaar extension itself when @x402/extensions is installed.

# pip install "x402[extensions]"
from x402.extensions.bazaar import OutputConfig, bazaar_resource_server_extension, declare_discovery_extension

server.register_extension(bazaar_resource_server_extension)

routes = {
    "GET /v1/quote/:symbol": RouteConfig(
        accepts=PaymentOption(scheme="exact", price="$0.005", network="eip155:8453", pay_to=os.environ["PAY_TO"]),
        description="Token price quote",
        extensions=declare_discovery_extension(output=OutputConfig(example={"symbol": "SOL", "usd": 150.25})),
    ),
}

The route is listed after its first payment. A route with path parameters is listed once, as /v1/quote/:symbol.

Staying listed

• Every 10 minutes, Cryptonly makes an unpaid request to each listed endpoint. It must answer 402 and ask to be paid to one of your addresses.
• An endpoint that fails 3 checks in a row, or passes none for 24 hours, is removed from the feed. It comes back once it passes again.
• To remove an endpoint yourself, turn off List publicly, or stop declaring discovery in code.
• You can list up to 50 endpoints per account.
• Endpoints of verified businesses are marked with extensions.cryptonly.verifiedMerchant: true.

Read the feed

The feed is public JSON in the x402 Bazaar format, at GET https://api.cryptonly.net/x402/discovery/resources:

curl "https://api.cryptonly.net/x402/discovery/resources?limit=20"

Open the feed

The sandbox feed is at https://sandbox-api.cryptonly.net/x402/discovery/resources. The feed needs no API key.

Or use the Bazaar client of the x402 SDK:

TypeScriptPython

import { HTTPFacilitatorClient } from '@x402/core/server';
import { withBazaar } from '@x402/extensions/bazaar';

const client = withBazaar(
  new HTTPFacilitatorClient({ url: 'https://api.cryptonly.net/x402' }),
);
const { items } = await client.extensions.bazaar.listResources();

# pip install "x402[extensions]"
from x402.extensions.bazaar import with_bazaar
from x402.http import FacilitatorConfig, HTTPFacilitatorClientSync

client = with_bazaar(HTTPFacilitatorClientSync(FacilitatorConfig(url="https://api.cryptonly.net/x402")))
items = client.extensions.bazaar.list_resources().items