How to Monetize Your MCP Server (x402 and Polar)

If your MCP server wraps a paid API, costs compute per call, or provides specialized capability, you probably want to charge for it. xmcp ships two monetization integrations: x402 for per-call micropayments and Polar for subscription-based access with license keys.

Two monetization models

x402: per-call micropayments

x402 is a protocol built by Coinbase on the long-reserved HTTP 402 status code. A client sends a signed crypto payment with each request; the server verifies it before executing the tool. No accounts, no subscriptions — just pay and use.

This model fits tools with unbounded usage patterns: an agent that calls a search tool hundreds of times in a session, a data enrichment tool where usage varies wildly per user, or any capability where a flat monthly fee doesn't match consumption.

Install the plugin:

npm install @xmcp-dev/x402

Add it to your config:

import { type XmcpConfig } from "xmcp";
import { x402Plugin } from "@xmcp-dev/x402";

const config: XmcpConfig = {
  http: true,
  plugins: [
    x402Plugin({
      facilitatorUrl: "https://x402.org/facilitator",
      payTo: process.env.WALLET_ADDRESS!,
      amount: 0.001, // USD per call
      asset: "USDC",
    }),
  ],
};

export default config;

From that point, every tool call requires a valid x402 payment header. Clients that support x402 (including AI agents built with compatible SDKs) handle the payment flow automatically.

See the full x402 integration guide for payment header details and testing.

Polar: subscription access

Polar is a developer-first monetization platform that handles subscriptions and license keys. The xmcp plugin validates Polar license keys on each request, so only paying subscribers can call your tools.

This model fits when you want predictable revenue — a monthly plan for teams, a one-time purchase for individuals, or tiered access based on subscription level.

Install the plugin:

npm install @xmcp-dev/polar

Add it to your config:

import { type XmcpConfig } from "xmcp";
import { polarPlugin } from "@xmcp-dev/polar";

const config: XmcpConfig = {
  http: true,
  plugins: [
    polarPlugin({
      accessToken: process.env.POLAR_ACCESS_TOKEN!,
      organizationId: process.env.POLAR_ORGANIZATION_ID!,
    }),
  ],
};

export default config;

Users include their license key with requests. The plugin validates it against Polar and rejects calls from expired or invalid keys.

See the full Polar integration guide for product setup, license key handling, and usage tracking.

Which model to choose

Use x402 when:

• Usage varies heavily per user or per session
• You want zero-friction access (no accounts, no sign-up)
• Your target users are autonomous agents that can handle crypto payments

Use Polar when:

• You want predictable, subscription-based revenue
• Your users are developers or teams buying access for a period
• You want usage analytics and customer management in a dashboard

You can also run both plugins simultaneously and route different tool groups to different payment models — though for most servers, one model is the right fit.

Next steps

• Pay-per-use MCP tools with x402 — detailed x402 setup and client-side payment flow.
• Integrating Polar with xmcp — Polar product setup, license keys, and usage tracking.
• Deployment docs — ship your monetized server to Vercel with zero config.