Explainers

The stack, in plain language

• What is the machine economy? — Software that discovers, pays, works and settles with other software — with humans setting budgets and rules.
• What is x402? — An open protocol that uses HTTP 402 so a client can pay a server, usually in USDC, and retry.
• How does HTTP 402 work? — A reserved status code. The interesting part is the payload, the retry, and who verifies payment.
• What is an agent wallet? — A spending envelope a machine can use, with policy, not a seed phrase pasted into a prompt.
• What is MCP? — A standard way for models to list and call tools. It is not itself a payment protocol.
• What is paid MCP? — Charging for a tool call. Today that charge is an overlay — often x402 or a vendor gateway — not a core MCP message type.
• How do agents pay for APIs? — Discover, read schema and price, receive 402, pay, retry, verify. No account required if the rail is designed that way.
• What is MPP? — The Machine Payments Protocol: Stripe and Tempo’s HTTP 402 standard for agents, designed to be rail-agnostic.
• What is autonomous procurement? — Software that buys inputs under a budget, a rights gate and an audit log — not an unconstrained agent with a credit card.
• Why stablecoins for agents? — A programmable dollar with public settlement, not a prediction about token prices.
• What is agent discovery? — How a machine finds something it can use — and whether that listing matches live behaviour.
• What is agent reputation? — Evidence that a machine payer or seller will behave, not a follower count.
• What is agent-to-agent commerce? — One piece of software hiring another, with payment, contract and delivery — not two chatbots role-playing.