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Machine Payments Protocol (MPP)

An open, HTTP-native payment standard co-authored by Stripe and Tempo Labs that enables autonomous AI agents to pay for digital resources using both stablecoins and traditional fiat rails within a single protocol.

Rail: Payment · Updated: 2026-06-05

What It Is

The Machine Payments Protocol (MPP) is an internet-native payment standard co-authored by Stripe and Tempo Labs that formalizes the long-dormant HTTP 402 "Payment Required" status code into a complete authentication scheme for machine-to-machine commerce. When an autonomous AI agent requests a paywalled digital resource — an inference call to a language model, a query to a premium financial database, a compute allocation — the host server responds with a cryptographic 402 challenge encoded in WWW-Authenticate headers. The agent reads the challenge, selects an optimal payment route from its available wallets, executes the transaction, and retries the request with mathematical proof of payment. The resource is delivered in a single exchange with no human intervention.

What distinguishes MPP from competing machine payment standards, particularly the Coinbase-led x402 protocol, is its dual-rail architecture and its session model. x402 is optimized for discrete, stateless on-chain settlements — one transaction per request. For agents making thousands of API calls per minute, the latency and cumulative gas fees of repeated blockchain broadcasts become prohibitive. MPP resolves this with a "session" intent: an agent pre-authorizes a maximum spending limit, then streams continuous off-chain micropayments against that limit. The final settlement is executed as a single aggregated transaction on the Tempo blockchain, which is purpose-built for sub-second deterministic finality without a volatile gas token.

MPP is also genuinely payment-method agnostic. A single server endpoint can accept payment over the Tempo Layer-1 blockchain (USDC stablecoin), the Lightning Network (Bitcoin), or Stripe's traditional card networks (fiat) simultaneously. Stripe's Shared Payment Tokens (SPTs) allow a human to delegate spending authority from a conventional Visa or Mastercard directly to an AI agent, which then streams fiat micropayments via Stripe's standard rails under the same MPP routing logic. This bridge between crypto and conventional finance is MPP's primary strategic differentiator — and Stripe's motivation for co-authoring it.

Real-World Example

Browserbase, a cloud infrastructure provider, uses MPP to let autonomous AI agents spin up headless web browsers for data scraping and automation tasks on demand. Instead of a developer pre-purchasing a SaaS subscription tier or managing rotating API keys, the agent pays a sub-cent USDC fee per individual browsing session via MPP precisely when the computing power is needed — no billing relationship, no contract, no human accountant.

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