Use Cases

AI agent tool use

AI agents need to access external data — search results, market data, code analysis, document parsing. With Crumb, an agent can discover and pay for API resources autonomously, without pre-configured API keys or billing relationships.

// Agent autonomously pays for search results
const result = await crumb.fetch('https://api.example.com/search', {
  method: 'POST',
  body: { query: 'latest research on quantum error correction' },
  maxPayment: 0.01, // refuse to pay more than 1 cent
})

The maxPayment ceiling ensures agents can't overspend — the SDK throws PRICE_EXCEEDED before signing if the price is too high.

Monetizing APIs

Any Express server can become a paid API in minutes. No Stripe integration, no billing system, no subscription management. Set a price per endpoint and start earning USDC.

const provider = createProvider({ sellerAddress: '0x...' })

app.get('/api/data', provider.require('$0.01'), handler)
app.get('/api/premium', provider.require('$0.50'), premiumHandler)

Payments settle through Circle Gateway. You receive USDC directly to your wallet.

Pay-per-use content

Instead of paywalls with monthly subscriptions, charge per article, per query, or per download. Users pay exactly for what they consume.

Machine-to-machine payments

IoT devices, automated pipelines, and background services that need to pay for resources without human approval. Deposit USDC into Gateway once, and the system handles payments automatically.

Peer-to-peer transfers

Crumb's web app supports direct P2P transfers using payment handles. Send USDC to @alice — gasless, instant, with QR code support.

Merchant checkout

Create payment links for fixed-amount purchases. Customers scan a QR code or click a link, sign a gasless transaction in their wallet, and the merchant receives a webhook confirmation.