MCP Payments Explained: x402, Stripe Machine Payments and Paid Tools

MCP payments let an AI agent pay for a tool call on the spot. The server answers an unpaid call with a "payment required" response that names the price. The agent's client pays, retries with proof of payment, and gets the result. Two protocols do this today: x402, an open standard built on HTTP status 402, and the Machine Payments Protocol (MPP) from Stripe and Tempo.

This matters for anyone selling small, frequent services to agents, such as data lookups or compute, where a subscription is too much. It also matters for anyone letting agents spend money, because a paying agent needs limits. This guide explains how both protocols work with MCP, based on docs checked on 2 November 2026.

Why agents need a new way to pay

Normal online payments assume a person. They fill in a form, create an account and confirm a card. Stripe's machine payments docs put it this way: "These flows require human input, which blocks agents from completing tasks autonomously."

Machine payments replace the form with a protocol. "Your server returns a payment challenge, the agent presents a valid payment credential, and Stripe settles the payment to your Stripe balance," per the same docs.

How x402 works

The x402 site describes it as "an open, neutral standard for internet-native payments." The core loop: "If a request arrives without payment, the server responds with HTTP 402, prompting the client to pay and retry."

The x402 GitHub repository, under the x402-foundation organization and licensed Apache-2.0, lists payment "schemes." exact moves a fixed amount. upto authorizes a maximum, with the final charge set at settlement. The x402 site says it is "blockchain-agnostic" and that "Stablecoin payments are the primary use case." It also says x402 "is free for the customer and the merchant," apart from "nominal payment network fees."

A facilitator is the service that checks and settles payments. Cloudflare's x402 docs say the facilitator at https://x402.org/facilitator is operated by Coinbase, exposes POST /verify and POST /settle, and "doesn't hold funds."

x402 inside MCP

MCP tool calls are not plain HTTP requests, so x402 needs an MCP version. Coinbase's MCP payments guide calls it the x402 MCP transport. The server replies to an unpaid call with a payment-required result. The client retries with payment attached in MCP metadata.

On the client side, Coinbase's TypeScript example wraps a standard MCP Client from @modelcontextprotocol/sdk with a wrapMCPClientWithPayment helper from @x402/mcp. Two settings matter:

• autoPayment: true pays and retries automatically on a 402. With false, the client stops so you can inspect the price.
• spendControls, commented in the example as "Bound what this agent can spend."

Coinbase also runs a discovery server, the Bazaar, with three tools: search_resources, proxy_tool_call and validate_endpoint. Its docs say "The endpoint is unauthenticated," and searching is free; only paid calls trigger payment.

Charging for a tool on Cloudflare

Cloudflare's guide to charging for MCP tools wraps an MCP server like this:

const server = withX402(
	new McpServer({ name: "PaidMCP", version: "1.0.0" }),
	X402_CONFIG,
);

The config names the network (base for production, base-sepolia for testing), a recipient wallet address and the facilitator URL. Paid tools are registered with server.paidTool( and a USD price such as 0.01. The docs say the handler runs only after payment succeeds, and unpaid calls get a 402 with payment requirements. A free tool, registered with server.registerTool(, can sit on the same server. The snippet above was checked against Cloudflare's docs on 2 November 2026; eSEOspace did not run it.

How Stripe fits in

Stripe introduced the Machine Payments Protocol on 18 March 2026 as "an open standard, internet-native way for agents to pay." It was co-authored with Tempo. Stripe users accept MPP payments through the PaymentIntents API, and payments appear in the Dashboard like any other.

Stripe's machine payments docs say it "works best with the Machine Payments Protocol (MPP) that is able to accept card and stablecoin payments. Stripe also supports stablecoin payments over the x402 protocol."

Other details from the same page:

• Cards. MPP accepts cards through Shared Payment Tokens (SPTs), "scoped grants that let an agent use a customer's payment method." Each SPT has usage and expiration limits.
• Minimums. 0.50 USD for card payments via SPTs; 0.01 USDC for stablecoin payments. MPP sessions can meter in sub-cent steps but settle at 0.01 USDC minimum.
• Availability. Stablecoin payments are available to businesses "in all US states, except New York," and by request in 30+ other countries.
• Refunds and reporting. Refunds work through the normal Refunds API, and payments "settle in fiat."
• Discovery. Stripe invites businesses to submit integrations for its Stripe Directory, "a catalog of tools and services that helps agents find your business."

Stripe also runs its own MCP server for account tasks. That is a different thing: see our Stripe MCP server profile.

x402 or Stripe MPP?

Stripe supports both, so a Stripe merchant does not have to choose only one.

Guardrails before you let an agent pay

Payments are the highest-risk action an agent can take. The MCP tools specification says there "SHOULD always be a human in the loop with the ability to deny tool invocations." For payments:

• Cap spending per call, per day and per vendor. Coinbase's client example includes spend controls for this reason.
• Turn off auto-payment until you trust a server. Review prices first.
• Use test networks such as Base Sepolia while building.
• Log every payment with the tool, price and result. See MCP audit logging.
• Vet servers before connecting a wallet. A malicious tool description can push an agent to pay. See MCP security risks.

Note that Claude's connector review criteria do not accept directory connectors that "Transfer money, cryptocurrency, or other financial assets."

Next step

If you plan to sell tools to agents, read how to monetize an MCP server to choose a model first. For payment-related servers you can connect today, see our list of MCP servers for payments. Our MCP development team can scope a paid tool with spending limits built in.

Frequently asked questions