x402

Fresh 🌱

AgentMail's x402 integration for HTTP-native payments

Getting started

x402 is an open payment protocol that enables HTTP-native payments. By integrating x402 with AgentMail, your agents can pay for API usage directly over HTTP without managing API keys or subscriptions.

X Layer

Agents on X Layer can pay for API usage directly over HTTP via x402. X Layer is an Ethereum Layer 2 network built with Polygon CDK, offering high throughput and near-zero gas fees.

Base URLs

To authenticate with x402 instead of an API key, you must use the x402-specific base URLs below. These replace the default AgentMail base URLs and route requests through the x402 payment layer.

Protocol	URL
HTTP	x402.api.agentmail.to
WebSocket	x402.ws.agentmail.to

Prerequisites

• A crypto wallet with USDC funds (EVM-compatible wallet on Base, or a Solana wallet)
• Node.js installed

Install dependencies

npm install agentmail @x402/fetch @x402/evm viem

npm install agentmail @x402/fetch @x402/svm @solana/kit @scure/base

Quickstart

import { privateKeyToAccount } from "viem/accounts";
import { x402Client } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm/exact/client";

import { AgentMailClient } from "agentmail";

// setup x402 client

const PRIVATE_KEY = "0x...";

const signer = privateKeyToAccount(PRIVATE_KEY);

const x402 = new x402Client();
x402.register("eip155:*", new ExactEvmScheme(signer));

// setup AgentMail client

export const client = new AgentMailClient({ x402 });

// create inbox

const inboxRes = await client.inboxes.create({
  username: `x402-${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],
});

import { createKeyPairSignerFromBytes } from "@solana/kit";
import { base58 } from "@scure/base";
import { x402Client } from "@x402/fetch";
import { ExactSvmClient, toClientSvmSigner } from "@x402/svm";

import { AgentMailClient } from "agentmail";

// setup x402 client

const PRIVATE_KEY = "base58-encoded-private-key...";

const keypair = await createKeyPairSignerFromBytes(
  base58.decode(PRIVATE_KEY)
);

const x402 = new x402Client();
x402.register("solana:*", new ExactSvmClient(toClientSvmSigner(keypair)));

// setup AgentMail client

export const client = new AgentMailClient({ x402 });

// create inbox

const inboxRes = await client.inboxes.create({
  username: `x402-${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 x402 client to AgentMailClient, the SDK automatically handles payment negotiation for each API request. If the server responds with a 402 Payment Required status, the x402 client signs a payment using your wallet and retries the request with the payment attached.

This means your agent can use the full AgentMail API (inboxes, messages, threads, attachments) without needing a traditional API key. Payment happens per-request over HTTP.

Resources

• x402 documentation
• AgentMail API reference
• WebSockets overview