TL;DR
- MPP (Machine Payments Protocol) is an open, HTTP-native standard co-authored by Stripe and Tempo, launched March 18, 2026, for programmatic agent-to-service payments.
- MPP uses
402 Payment Requiredchallenges like x402, but adds lifecycle primitives: subscriptions, streaming usage, cancellations, and reconciliation—plus multi-method settlement (stablecoins, cards via Shared Payment Tokens, BNPL). - Tempo, a payments-focused L1 blockchain, is MPP's default stablecoin settlement network (~500ms finality, sub-cent fees); Stripe merchants can accept MPP via PaymentIntents in a few lines of code.
- MPP sits in Stripe's Agentic Commerce Suite alongside ACP, MCP integrations, and x402 support—MPP is the merchant-grade machine payment wire for existing Stripe accounts.
- For B2B SaaS on Stripe, MPP is the path to bill agents without rebuilding fraud, dispute, and accounting plumbing.
What Is MPP? — A Working Definition
The Machine Payments Protocol (MPP) is an open standard for agents and services to coordinate payments programmatically over HTTP. Stripe announced MPP on March 18, 2026—the same day Tempo's mainnet went live—describing it as an "internet-native way for agents to pay" for microtransactions, recurring charges, streaming usage, and more.
MPP is not a Stripe-only proprietary API, though Stripe is a primary implementer. Tempo co-authored the normative specification and documents MPP as the default way to charge on Tempo's chain. The protocol extends the bare x402 pattern with payment lifecycle semantics merchants need in production: not just "pay once per request," but subscriptions, session-based streaming, balance reconciliation, and cancellation.
If x402 is the HTTP payment handshake, MPP is the full merchant stack expression of that handshake for teams already on Stripe—or willing to settle stablecoins on Tempo.
How MPP Works: Challenges, Credentials, and Receipts
MPP follows an inline payment pattern familiar from x402:
- A client (agent, app, or human) requests a paid resource.
- The server responds with
402and a Challenge describing price, currency, and accepted payment methods. - The client pays and retries with a Credential (signed authorization).
- The server verifies payment and returns the resource with a Receipt.
Tempo's documentation distinguishes two intent patterns on-chain:
| Pattern | Latency | Best for |
|---|---|---|
| Charge | ~500ms on-chain confirmation | Single API calls, one-off content access |
| Session | Near-zero via off-chain vouchers | LLM APIs, metered services, streaming usage |
Session billing amortizes on-chain cost across many requests—critical for inference and token-metered APIs where per-request chain settlement would be uneconomical.
Stripe's implementation exposes MPP through libraries like mppx, registering payment methods (Stripe Shared Payment Tokens, Tempo charges) and wrapping handlers that return 402 challenges or settled responses.
Shared Payment Tokens and Multi-Method Settlement
MPP's differentiation from "402 only" is multi-method settlement through a common wire shape:
- Stablecoins via x402-compatible signatures on Tempo (and extensible to other networks)
- Cards via Shared Payment Tokens (SPTs)—scoped, limited-use tokens that relay a buyer's payment method to a seller without exposing PAN data to the agent
- BNPL via Klarna or Affirm where supported
Shared Payment Tokens carry scoped limits merchants can introspect before charging—Visa card SPTs enforce amount caps at the network level (Stripe Sessions 2026 demo: a $25 token rejects a $50 charge). Card SPT minimum is $0.50; stablecoin minimum is 0.01 USDC. Merchants validate with npx mppx validate for end-to-end discovery, challenge, and settlement testing.
Session intent (formalized on mpp.dev) supports streaming LLM and metered APIs via off-chain vouchers, with on-chain settlement batched—paired at Stripe Sessions 2026 with Metronome usage metering. subscription intent remains in spec development as of mid-2026; recurring SaaS billing still flows through Stripe Billing for most merchants today.
Tempo, Streaming, and Stripe Dashboard Integration
Tempo launched mainnet alongside MPP as a payments-optimized L1 (co-developed with Paradigm, Stripe-backed). Sub-cent fees and ~500ms finality target agent micropayments and per-request billing—constraints general-purpose chains handle poorly at scale.
At Sessions 2026 (April 29–30, 2026), Stripe added streaming payments as a first-class MPP primitive: real-time billing against a stablecoin balance for AI products that consume resources continuously.
For Stripe merchants, acceptance is intentionally low-friction: enable MPP via PaymentIntents API and existing Dashboard workflows—inheriting Stripe's fraud, dispute, and accounting machinery rather than standing up parallel agent billing ops. That is MPP's core B2B SaaS value proposition: agent buyers, human merchant rails.
MPP in Stripe's Agentic Commerce Suite
Stripe positions MPP inside a broader Agentic Commerce Suite:
| Component | Role |
|---|---|
| ACP | Retail checkout sessions for ChatGPT Instant Checkout |
| MPP | HTTP-native machine payments for APIs and services |
| x402 support | Interop with Linux Foundation x402 ecosystem |
| MCP integrations | Tool-level commerce for agent runtimes |
| Agentic Commerce Suite | Merchant onboarding for agent channels |
Teams selling through ChatGPT implement ACP; teams selling API access to agents implement MPP or x402. Many will need both surfaces over time.
MPP shares signature substrates with x402 (EIP-3009, Permit2 for off-chain authorization)—the protocols are compatible at the crypto layer, not forked competitors.
MPP vs x402 and AP2
- MPP vs x402: Same HTTP 402 transport idiom; MPP adds Stripe/Tempo lifecycle (subscriptions, streaming, SPT cards) and merchant Dashboard integration. Pure x402 is thinner and facilitator-agnostic.
- MPP vs AP2: MPP settles payment; AP2 proves delegated human authorization via mandates. High-trust enterprise flows may compose both.
For agent-to-agent micropayments where neither party is a registered Stripe merchant, x402 alone may suffice. For registered merchants billing agent traffic with card and stablecoin options plus dispute handling, MPP is the pragmatic choice.
What MPP Means for B2B SaaS Merchants
MPP matters when your product is consumed by software runtimes, not only human users in a dashboard.
Metered APIs and MCP tools map cleanly to Charge or Session intents—agents pay per call without OAuth signup flows.
Existing Stripe merchants avoid parallel billing systems; MPP charges flow through PaymentIntents with familiar reconciliation.
Risk teams get SPT limits and merchant scoping instead of sharing raw payment methods with agent code.
Gaps remain: enterprise procurement, tax invoicing, and multi-currency accounting may still require your existing subscription stack—smart routing for human renewals and MPP for agent usage can coexist. MPP does not replace MoR vs PSP decisions; it adds a collection mode.
Clink's Agentic Payments (Early Access) addresses the buyer-side harness—scoped caps and audit for agents spending on third-party APIs—while MPP addresses the seller-side HTTP charge. Complementary layers in a growing stack.
Conclusion
MPP is Stripe and Tempo's answer to a specific question: how do registered merchants bill agents with the same fraud, dispute, and ops tooling they use for humans—without a checkout page? HTTP 402 challenges, Shared Payment Tokens, and Tempo stablecoin settlement make that answer concrete.
Evaluate MPP if you are on Stripe and agent traffic is becoming material. Evaluate x402 if you need maximum facilitator neutrality or lightweight agent-to-agent transfers. Evaluate AP2 when authorization audit trails are non-negotiable. The agent payment future is layered; MPP is the merchant-native layer.
Retail catalog checkout on ChatGPT, Gemini, or Copilot uses ACP and UCP—not MPP. For live enablement by surface, platform, and processor, see our AI shopping channel list, commerce platform enablement list, and PSP agentic product list rather than inferring status from MPP documentation alone.