The Machine Payment Protocol (MPP) is an open standard for machine-to-machine payments. It rides on plain HTTP, so any agent that can make a request can make a payment — no SDK lock-in, no bespoke integration per provider.
The core idea
When an agent requests a paid resource, the server can respond with an HTTP 402 challenge describing the price and accepted methods. The agent selects a method, settles, and retries with proof of payment. The whole exchange is a few round-trips and completes in milliseconds.
Why a protocol, not a processor
A processor ties you to one rail. MPP is a thin negotiation layer above the rails: USDC via Circle Nanopayments, card networks, or anything else a provider chooses to accept.
- Method-agnostic — fiat and crypto settle through the same handshake.
- Stateless — no pre-funded accounts required between counterparties.
- Composable — every Aperture endpoint speaks it natively.
402 was reserved for "Payment Required" in 1997. Agents are the first clients that actually need it.
On Aperture, MPP is on by default. Your agent negotiates and settles automatically — you just set the budget.
Written by Diego Alvarez
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