Name the seller in the 402: x402-merchant extension

merchant.js

@@ -0,0 +1,30 @@
+// Who sells this, for x402 discovery lists. GoPlausible's catalog reads the
+// "x402-merchant" extension of a 402 challenge (name, website, logo, categories)
+// when it settles a payment, and shows it on the merchant: one per pay-to
+// address, which all four fizzl.eu services share on Algorand. So the info is
+// the same on every fizzl.eu service.
+const MERCHANT = {
+  name: 'Fizzl',
+  website: 'https://fizzl.eu',
+  logo: 'https://fizzl.eu/logo-512.png',
+  categories: ['ai-agents', 'security', 'trading-signals', 'developer-tools', 'x402', 'algorand'],
+};
+
+const merchantExtension = {
+  'x402-merchant': {
+    info: MERCHANT,
+    schema: {
+      $schema: 'https://json-schema.org/draft/2020-12/schema',
+      type: 'object',
+      required: ['name'],
+      properties: {
+        name: { type: 'string' },
+        website: { type: 'string' },
+        logo: { type: 'string' },
+        categories: { type: 'array', items: { type: 'string' } },
+      },
+    },
+  },
+};
+
+module.exports = { MERCHANT, merchantExtension };

server.js

@@ -11,6 +11,7 @@ const { ExactSvmScheme } = require('@x402/svm/exact/server');
 const { createFacilitatorConfig } = require('@coinbase/x402');
 const { fizzlCors } = require('./fizzl-cors');
 const { declareDiscoveryExtension } = require('@x402/extensions/bazaar');
+const { merchantExtension } = require('./merchant');
 const { McpServer, createMcpHandler } = require('@modelcontextprotocol/server');
 const { z } = require('zod/v4');
 const { createMediaCache } = require('./media');
@@ -241,14 +242,14 @@ if (x402PayTo) {
       description: "Check an EVM wallet's live token/NFT approvals and get a plain-language verdict (SAFE, CAUTION or RISK) with an explanation",
       mimeType: 'application/json',
       ...serviceMetadata,
-      extensions: checkWalletDiscovery
+      extensions: { ...checkWalletDiscovery, ...merchantExtension }
     },
     'POST /api/explain': {
       accepts: acceptsFor(x402ExplainPrice),
       description: 'What would signing this allow? Paste a wallet approval, transaction or typed-data signature before someone signs it: returns a SAFE, CAUTION or RISK verdict with a short plain-language explanation of what it gives away',
       mimeType: 'application/json',
       ...serviceMetadata,
-      extensions: explainDiscovery
+      extensions: { ...explainDiscovery, ...merchantExtension }
     }
   }, x402Server))));
 

test/algorand.test.js

@@ -36,7 +36,10 @@ async function acceptsWith(env) {
     for (let i = 0; i < 50; i++) {
       try {
         const res = await fetch(`http://127.0.0.1:${port}/api/check-wallet`, { method: 'POST', headers: { 'content-type': 'application/json' }, body: '{}' });
-        if (res.status === 402) return JSON.parse(Buffer.from(res.headers.get('payment-required'), 'base64').toString()).accepts;
+        if (res.status === 402) {
+          const challenge = JSON.parse(Buffer.from(res.headers.get('payment-required'), 'base64').toString());
+          return Object.assign(challenge.accepts, { extensions: challenge.extensions });
+        }
       } catch { /* not up yet */ }
       await new Promise((r) => setTimeout(r, 200));
     }
@@ -57,6 +60,9 @@ test('with ALGORAND_PAY_TO: $0.04 in USDC (ASA 31566704) on Algorand, with the A
   assert.equal(algo.amount, '40000');
   assert.equal(algo.extra.feePayer, FEE_PAYER, 'not the URL facilitator\'s');
   assert.ok(accepts.some((a) => a.network === 'eip155:8453'), 'Base still offered');
+  // GoPlausible names the seller (one merchant per Algorand pay-to) from this.
+  assert.equal(accepts.extensions['x402-merchant'].info.name, 'Fizzl');
+  assert.equal(accepts.extensions['x402-merchant'].info.logo, 'https://fizzl.eu/logo-512.png');
 });
 
 test('without ALGORAND_PAY_TO, or "off": no Algorand', async () => {