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# API monetization \[Per-request payments at the protocol level]

MPP replaces API keys, subscription tiers, and billing dashboards with a single protocol-level primitive: [HTTP `402`](/protocol/http-402). You set a price on your endpoint, and any client—human, app, or coding agent—pays per request. No signup, no plan selection, no payment form.

## The problem with API keys and subscriptions

Traditional API monetization requires developers to create an account, generate API keys, pick a pricing tier, and enter payment details before making a single request. Each step adds friction and increases drop-off.

For coding agents, this model breaks entirely. Agents can't fill out signup forms, navigate billing dashboards, or manage API key rotation. They need a payment interface that works at the HTTP level—not the browser level. See [agentic payments](/use-cases/agentic-payments) for more on how MPP solves this.

## Monetize your API with MPP

Add a few lines of middleware to your API, set a price per endpoint, and start accepting payments. When a client hits a paid endpoint, your server returns a `402` Challenge with the price and accepted payment methods. The client pays and retries—your server verifies the Credential and returns the response with a Receipt.

There's no billing dashboard to build, no user database to manage, no API key infrastructure to maintain. MPP supports stablecoins, cards, and Lightning—clients pay with whatever rail they have.

## Pricing models

MPP supports multiple pricing strategies out of the box:

* **Per-request charges**—Set a fixed price per endpoint. Each request is a standalone payment.
* **Pay-as-you-go sessions**—Open a session for streaming or high-frequency APIs. Clients pay incrementally via off-chain vouchers with on-chain settlement. This is what makes [micropayments](/use-cases/micropayments) viable.
* **Split payments**—Route portions of each payment to multiple recipients, enabling marketplace and referral models.

## Next steps

[Add payments to your API](/quickstart/server) — Start charging in minutes

[Accept pay-as-you-go payments](/guides/pay-as-you-go) — Session-based billing for high-frequency APIs

[Proxy an existing service](/guides/proxy-existing-service) — Add payments without changing your API code