MPP

Fresh 🌱

AgentMail's MPP integration for machine-to-machine payments via Stripe

Getting started

MPP (Machine Payments Protocol) is Stripe's open protocol that enables machine-to-machine payments. By integrating MPP with AgentMail, your agents can pay for API usage directly without managing API keys or subscriptions.

Base URLs

To authenticate with MPP instead of an API key, you must use the MPP-specific base URLs below. These replace the default AgentMail base URLs and route requests through the MPP payment layer.

Protocol	URL
HTTP	mpp.api.agentmail.to
WebSocket	mpp.ws.agentmail.to

Prerequisites

• A crypto wallet with funds (EVM-compatible wallet)
• Node.js installed

Install dependencies

npm install agentmail mppx viem

Quickstart

import { privateKeyToAccount } from "viem/accounts";
import { Mppx, tempo } from "mppx/client";

import { AgentMailClient } from "agentmail";

// setup MPP client

const PRIVATE_KEY = "0x...";

const account = privateKeyToAccount(PRIVATE_KEY);

export const mppx = Mppx.create({ methods: [tempo({ account })] });

// setup AgentMail client

export const client = new AgentMailClient({ mppx });

// create inbox

const inboxRes = await client.inboxes.create({
  username: `mpp-${Date.now()}`,
});
console.log("Created inbox: ", inboxRes.inboxId);

// subscribe to inbox

const socket = await client.websockets.connect();
console.log("Connected to websocket");

socket.on("message", async (event) => {
  if (event.type === "subscribed") {
    console.log("Subscribed to", event.inboxIds);
  } else if (event.type === "event" && event.eventType === "message.received") {
    console.log("Received message from: ", event.message.from);
  }
});

socket.sendSubscribe({
  type: "subscribe",
  inboxIds: [inboxRes.inboxId],
});

How it works

When you pass an mppx client to AgentMailClient, the SDK automatically handles payment negotiation for each API request. The MPP client signs payments using your wallet, enabling your agent to pay per request seamlessly.

This means your agent can use the full AgentMail API (inboxes, messages, threads, attachments) without needing a traditional API key. Payment happens per-request via Stripe's Machine Payments Protocol.

Resources

• MPP documentation
• AgentMail API reference
• WebSockets overview