MPP Protocol

4SEC supports MPP (Machine Payment Protocol) as an alternative payment method alongside x402.

What is MPP?

MPP is a machine-native payment protocol built on Tempo, Stripe's purpose-built blockchain for stablecoin payments. It is designed for automated, high-frequency API micropayments.

• Network: Tempo (Stripe's blockchain)
• Token: USDC on Tempo
• Discovery: mppscan.com
• Target: AI agents, bots, and automated systems

How MPP Works

When a client sends an unauthenticated request to a paid 4SEC endpoint, the API returns a 402 Payment Required response with an WWW-Authenticate header:

HTTP/1.1 402 Payment Required
WWW-Authenticate: Payment id="...", realm="api.foursec.xyz",
  method="tempo", intent="pay",
  request="<base64-encoded-payment-request>",
  expires="2026-07-08T15:00:00Z"

The client decodes the request field, creates a Tempo USDC transfer, and retries with the payment proof.

MPP vs x402

Feature	x402	MPP
Network	Base (Coinbase)	Tempo (Stripe)
Token	USDC on Base	USDC on Tempo
Discovery	x402scan.com	mppscan.com
Standard	RFC-like x402	MPP spec
Gas	Gasless (sponsored)	Gasless

Both protocols are interoperable — 4SEC supports both simultaneously. Your client library determines which one is used based on what it supports.

Getting Started with MPP

1. Get USDC on the Tempo network
2. Use an MPP-compatible client library or wallet
3. Make requests to 4SEC endpoints — the client handles payment automatically

Discovery

4SEC is registered on mppscan.com. Scanners can discover all MPP-compatible endpoints, pricing, and payment requirements automatically via the WWW-Authenticate challenge header.

Related

• How x402 Works — the other payment protocol
• Pricing — costs for all endpoints
• Wallet Setup — set up your wallet