Merchant Demo Store
API endpoints paywalled with Crumb. Connect your wallet or use the SDK to pay per request.
Gateway Balance
Gateway Available
— USDC
Wallet Balance
— USDC
Service Discovery (Free)
GET
/api/services
FREE
Returns all available endpoints, prices, and how to call them.
Paid Endpoints
GET
/api/joke
$0.001
Get a random programming joke. Payment required via x402.
or
POST
/api/search
$0.001
Search for information. Enter a query and pay to get results.
or
GET
/api/premium-fact
$0.01
Get a premium curated fact. Higher price for premium content.
or
Seller Address
0x2e12E5C0eA814F6f7B08eF67aBb7aB5C25468eFB
Agent (SDK)
Browser (Wallet)
Agent Usage
An agent can discover and transact with this store using the Crumb SDK:
import { Crumb } from 'crumb-alpha-sdk'
const crumb = new Crumb({ privateKey: process.env.PRIVATE_KEY })
// 1. Discover available services
const services = await fetch('https://your-store.vercel.app/api/services')
// 2. Call a paywalled endpoint — payment is automatic
const result = await crumb.fetch('https://your-store.vercel.app/api/joke', {
method: 'GET',
maxPayment: 10000,
})
console.log(result.data) // { joke: "..." }
console.log(result.txHash) // on-chain settlement
Browser Wallet Flow
Connect MetaMask above, then click "Buy" on any endpoint. The x402 flow works like this:
1. Browser requests the endpoint
2. Server responds with 402 Payment Required
3. Browser parses payment requirements from header
4. MetaMask signs an EIP-712 authorization (no gas needed!)
5. Browser retries the request with the signed payment
6. Server verifies payment and returns the content
Payments use Circle Gateway batching — signatures are gasless. You need USDC deposited in the Gateway for your connected wallet.