Payment as an HTTP primitive
The Machine Payments Protocol (MPP) is an open standard for machine-to-machine payments, co-authored by Stripe and Tempo. It launched with Tempo mainnet on 18 March 2026.
MPP builds on the long-dormant HTTP 402 Payment Required status code. The flow happens within a single request cycle, with no redirects or webhooks:
- A client requests a resource.
- The server responds with
402 Payment Requiredand a price challenge. - The client pays and retries with payment credentials.
- The server returns the resource with a receipt.
Because payment is inline, any client — an AI agent, an app, or a human — can pay for a service with no API keys, billing accounts, or signup flow.
Why it matters for agents
MPP is built for a world where software, not just people, pays for things. An autonomous agent can discover a priced endpoint, pay for exactly what it consumes, and move on — without a human provisioning an account first.
Payment methods supported at launch include stablecoins on Tempo (the primary path), cards via Stripe, and Bitcoin via the Lightning Network, with more planned. The open specification lives in the public mpp-specs repository, and SDKs exist for Rust and Python.
The Payments Directory
Services that accept MPP are listed in the Payments Directory at mpp.dev. It launched with 100+ members across model providers, developer infrastructure, compute, and data — named members include Alchemy, Dune, Anthropic, OpenAI, and Shopify.
Adoption has extended beyond launch partners: RedotPay — which reports 7.5M users across 100+ countries — integrated MPP to bring agentic payments to its users in May 2026.