AgentBill

The "Stripe" for x402 — make any API payable by an AI agent in two lines of code.

Built on Base · Powered by x402 V2 · Settles in USDC

Live demo: agent-billmiddleware-production.up.railway.app · Proof of payment: Basescan tx

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The Problem

The internet is shifting from humans clicking buttons to AI agents calling APIs. But most APIs still require a credit card, a monthly subscription, or a complex API key setup that an agent can't navigate.

The x402 protocol (by Coinbase) fixes this: a server returns 402 Payment Required and the agent pays instantly in USDC — no signup, no OAuth, no human in the loop.

The catch: wiring up x402 from scratch means configuring resource servers, registering payment schemes, handling CAIP-2 network IDs, and getting the headers right. Most developers won't bother.

AgentBill makes it two lines.

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What is AgentBill?

A middleware SDK that wraps x402 V2 so developers can add a payment wall to any Express route with minimal setup.

import { agentBill, requirePayment } from "@agent-bill/middleware";

agentBill.init({ receivingAddress: "0xYours", network: "base-sepolia" });

app.get(
  "/api/data",
  requirePayment({ amount: "0.01", currency: "USDC" }),
  handler
);

That's it. Your API now accepts USDC payments from any AI agent or x402-compatible client.

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How It Works

AI Agent                    Your API (AgentBill)         x402.org Facilitator
    │                               │                            │
    │── GET /api/data ─────────────►│                            │
    │◄── 402 + PAYMENT-REQUIRED ────│                            │
    │                               │                            │
    │  [signs payment authorization]│                            │
    │                               │                            │
    │── GET /api/data ──────────────│                            │
    │   + PAYMENT-SIGNATURE header  │── verify ─────────────────►│
    │                               │◄── valid ──────────────────│
    │◄── 200 + data ────────────────│                            │

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Project Structure

agent-bill/
├── packages/
│   ├── middleware/        # @agent-bill/middleware — Express + Next.js payment wall
│   └── client/           # @agent-bill/client — payment-enabled fetch for agents
├── examples/
│   ├── testnet/express-quickstart/   # Base Sepolia demo
│   └── mainnet/express-quickstart/   # Base mainnet demo (deployed on Railway)
└── README.md

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Getting Started

Install

npm install @agent-bill/middleware

Usage

import express from "express";
import { agentBill, requirePayment } from "@agent-bill/middleware";

const app = express();

agentBill.init({
  receivingAddress: "0xYourWalletAddress",
  network: "base-sepolia", // or "base-mainnet"
});

app.get(
  "/api/weather",
  requirePayment({
    amount: "0.01",
    currency: "USDC",
    description: "Weather data",
  }),
  (req, res) => {
    res.json({ city: "New York", temp: "72°F" });
  }
);

app.listen(3000);

Next.js (App Router)

// app/api/weather/route.ts
import { withPayment } from "@agent-bill/middleware/next";

async function handler(req: NextRequest) {
  return NextResponse.json({ city: "New York", temp: "72°F" });
}

export const GET = withPayment({ amount: "0.01", currency: "USDC" }, handler);

Call agentBill.init() once in instrumentation.ts before any requests are handled.

See packages/middleware/README.md for full API docs.

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Roadmap

• @agent-bill/middleware v0.1 — Express payment wall (x402 V2)
• @agent-bill/middleware — Next.js App Router support (withPayment)
• Mainnet deployment on Railway — live 402 paywall
• @agent-bill/client v0.1 — payment-enabled fetch for AI agents
• Hono adapter — Cloudflare Workers edge support
• Dashboard — payment analytics per endpoint

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Why Base?

Base has near-zero gas fees, making micro-transactions (e.g. $0.01) economically viable. AgentBill is designed for the Base ecosystem — settles in USDC, compatible with Coinbase AgentKit and the x402 facilitator out of the box.

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License

MIT

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AgentBill is not affiliated with Coinbase. x402 is an open protocol.