Vercel App Mpp is the public gateway for the Machine Payments Protocol (MPP), a stablecoin-based payment layer for AI agents and other automated clients. Hosted at https://mpp-gateway.vercel.app/, the gateway sits in front of more than forty third-party APIs and lets a client pay per request with a Tempo stablecoin instead of holding API keys.
The flow is built around HTTP 402 Payment Required. A client makes a normal HTTP request to an MPP endpoint; if payment is required the gateway returns a 402 with the price and payment instructions. A Tempo CLI running on the client signs and settles the payment automatically, the gateway proxies the call to the upstream API, and the client receives the response together with a signed Payment-Receipt. An AI agent can reach Stripe, GitHub, Twilio, Plaid, Massive (stocks) and Stripe Climate without ever storing a secret API key.
Vercel App Mpp currently exposes 88 endpoints across 11 categories and 5 live services. Each endpoint lists its price in USD. The site publishes an llms.txt and an All Routes page so AI agents can discover endpoints programmatically. The gateway runs on Vercel's edge network, charges transparent per-request prices, and ships with a public GitHub repository. It is one of the first concrete implementations of machine-to-machine stablecoin payments for general API access.
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