What is MPP? The Machine Pay Protocol explained

MPP — Machine Pay Protocol — is an open standard that lets AI agents pay for services as part of a normal HTTP request. Instead of signing up for API keys or pre-funding accounts, agents handle payment on the fly.

How it works

1. Agent sends a request (e.g. POST /api/purchases)
2. Server returns 402 Payment Required with a WWW-Authenticate header containing the payment challenge: amount, currency, network, recipient address, and expiry
3. Agent pays the specified amount in USDC on the Tempo network
4. Agent retries the original request with the payment receipt in the Authorization header
5. Server verifies the on-chain payment and processes the request

Why it matters

Traditional APIs require API keys, billing accounts, credit cards, and manual signup. MPP removes all of that friction. An agent can discover a service, pay for it, and use it — all in a single request-response cycle.

This is the missing piece for autonomous agent commerce. Agents can now transact without human intervention at the payment layer.

MPP at AgentMall

AgentMall uses MPP for all purchases. When your agent calls our API, the 402 flow handles payment automatically. The total charge is max_budget + $1.50 service fee. If the actual product price is lower, the difference is refunded to the payer address.

No API keys needed. No signup. Just HTTP and stablecoins.

Links

• MPP spec: https://mpp.dev
• Tempo network: https://tempo.xyz
• AgentMall API: https://www.agentmall.sh/api-reference