Stripe and Tempo launched the Machine Payments Protocol (MPP) - the third major payment protocol for the agentic economy. Visa released a card-native specification.
| Dimension | Traditional UX | Agentic Experience Design (AXD) |
|---|---|---|
| Primary material | Attention and affordance | Trust and delegation |
| User state | Present, navigating | Absent, delegating |
| Design output | Screens and interfaces | Outcomes and constraints |
| Temporal model | Session-based | Relationship-based |
| Success metric | Task completion | Trust calibration |
The Machine Payments Protocol (MPP) is an open standard for machine-to-machine payments, co-authored by Stripe and Tempo and launched on March 18, 2026. MPP provides a specification for autonomous AI agents and services to coordinate payments programmatically over HTTP, enabling microtransactions, recurring payments, and agent-to-service commerce. The protocol follows a four-step flow: an agent requests a resource, the service responds with a payment requirement, the agent authorises payment, an
ACP (Agentic Commerce Protocol), co-authored by Stripe and OpenAI, is a buyer-side protocol that enables agents to discover products, compare options, and complete purchases on behalf of humans. MPP is a seller-side protocol that enables services to accept payments from agents programmatically. x402, created by Coinbase, is an HTTP-native payment protocol that uses the 402 Payment Required status code to embed payment requirements directly into web requests. Together, they address different laye
The Machine Payments Protocol (MPP) is an open standard for machine-to-machine payments, co-authored by Stripe and Tempo and launched on March 18, 2026. MPP provides a specification for autonomous AI agents and services to coordinate payments programmatically over HTTP, enabling microtransactions, recurring payments, and agent-to-service commerce. The protocol follows a four-step flow: an agent requests a resource, the service responds with a payment requirement, the agent authorises payment, an
ACP (Agentic Commerce Protocol), co-authored by Stripe and OpenAI, is a buyer-side protocol that enables agents to discover products, compare options, and complete purchases on behalf of humans. MPP is a seller-side protocol that enables services to accept payments from agents programmatically. x402, created by Coinbase, is an HTTP-native payment protocol that uses the 402 Payment Required status code to embed payment requirements directly into web requests. Together, they address different laye
On March 18, 2026, Stripe and Tempo published the Machine Payments Protocol - an open standard for machine-to-machine payments over HTTP. The same day, Visa released a card-native specification and software development kit extending MPP to support tokenised card credentials on its global network. Within twenty-four hours, agents could pay for browser sessions, physical mail, sandwiches, and climate offsets without a single human touching a checkout page. The protocol is elegant. An agent requests a resource. The service names a price. The agent pays. The resource is delivered. Four steps. No account creation, no pricing page navigation, no subscription tier selection, no billing setup. Commerce reduced to its protocol-level essence: request, price, pay, deliver. But MPP does not arrive in isolation. It is the third major payment protocol to emerge for the This essay analyses what MPP is, what it solves, what it leaves undesigned, and why the protocol proliferation problem - the simultaneous emergence of multiple incompatible payment standards for autonomous agents - is the defining infrastructure challenge of The Four-Step Architecture of Machine Payments The Machine Payments Protocol is built on a deliberately minimal architecture. Its designers - Jeff Weinstein, Stripe's Product Lead for Agentic Commerce, and Steve Kaliski, Stripe's Engineering Lead for Agentic Commerce - describe it as "an open standard, internet-native way for agents to pay." The protocol operates in four steps. An agent sends an HTTP request to a service, API, Model Context Protocol (MCP) server, or any HTTP-addressable endpoint. The request is indistinguishable from any other HTTP request - the protocol does not require the agent to identify itself as non-human at this stage. The service responds with a payment requirement. This is the protocol's key innovation: instead of presenting a pricing page, a subscription tier selector, or a checkout flow designed for human navigation, the service ret