MPP · Machine Payments Protocol
A card-rail protocol for machine-to-machine payments.
MPP is Stripe and Tempo's machine-payments protocol — a counterpart to x402 that brings card-network settlement (and Tempo's clearing layer) into agentic, programmatic flows. Where x402 leans on stablecoins, MPP keeps agents on Visa/Mastercard rails with merchant compatibility, dispute primitives, and Stripe-grade fraud tooling.
The four things MPP actually delivers.
- Defines a machine-to-machine payment handshake on existing card rails.
- Issues scoped, agent-bound credentials via Stripe + Tempo clearing.
- Carries merchant-friendly metadata (MCC, scope, dispute hooks).
- Slots into existing Stripe SDKs and merchant integrations.
The flow, end to end.
Agent registers
A scoped credential is issued with merchant + spend constraints.
Merchant accepts
Existing Stripe checkout receives an MPP-tagged payment.
Tempo clears
Tempo provides programmable clearing + dispute primitives.
Settlement
Funds move on the card network with full reconciliation metadata.
A robot waiter at a restaurant chain hands the kitchen a special ID badge. The kitchen still uses its normal card machine, but the badge says exactly which orders this robot can place and how much it can spend. That is MPP — agents on the existing card network with badges instead of human cards.
One policy plane across MPP + x402
Most agents will need both rails — cards for retail merchants, x402 for APIs. xpay enforces the same spend limits and audit trail across either rail so you do not maintain two governance stacks.
How Smart Proxy works →What MPP ships, what it does not, and what bridges the gap.
Card-rail compatibility, dispute + chargeback primitives, Stripe ecosystem reach.
Multi-rail abstraction, on-chain auditability, cross-protocol policy.
A single policy plane that works across MPP, x402 and ACP — same budget caps, same audit trail, no matter the rail.
MPP compared.
MPP vs x402
MPP rides the card network with Tempo clearing; x402 settles in stablecoins over HTTP. MPP wins on merchant ubiquity, x402 wins on programmability, latency, and zero-fee rails.
MPP vs ACP
ACP defines the conversational checkout shape (ChatGPT-style). MPP defines the underlying card-rail credential. ACP can settle through MPP — they are not exclusive.
Other protocols in the same neighbourhood.
x402
Native HTTP payments for APIs and AI agents.
AP2
Governance standards for agent payments — multi-rail.