# Meter Your API Charge AI agents per call — no API keys to hand out, no invoicing. Your endpoint asks for payment, the agent pays, and you get settled. ## How it works 1. An agent calls your endpoint. 2. Your endpoint returns `402 Payment Required` with a price. 3. The agent pays — its SDK handles it — and the facilitator verifies and settles the payment. 4. Your endpoint returns the data. ## Register your API Register your endpoint as a resource server. That hands back an API key the facilitator uses to verify and settle incoming payments — store it, it's shown once. ```typescript import { FacilitatorClient } from "@newton-xyz/isaac"; const facilitator = new FacilitatorClient({ baseUrl: process.env.PLATFORM_API_URL!, operatorApiKey: process.env.OPERATOR_API_KEY!, }); const { server, apiKey } = await facilitator.createServer({ name: "Weather API", recipientAddress: "0xYourPayoutAddress", // where settled payments land vaultAddress: "0xYourVault", // the custody vault backing settlement }); ``` Prefer clicking to code? Register the same server from the dashboard. ## Ask for payment On a paid route, respond with `402` and the payment requirements — the price, the token, and where to pay. The agent's SDK reads them, pays, and retries the request. The header format is defined by the [x402 protocol](https://x402.org). ## Next * **[Pay for an API](/guides/pay-for-an-api)** — the same exchange, seen from the agent's side.