x402 Micro Tollgate

x402-micro-tollgate

Visa for AI agents that can’t hold a card.

Second-scale settlement bridge for agent traffic — the Web3 tollbooth that clears USDC micropayments and takes 0.1%.

为千万级无支付能力的 AI Agent 提供秒级过桥清算，抽成 0.1% 的 Web3 版 Visa 收费站

Security backed by Coinbase CDP. We don't touch your keys or settle payments on custom cryptography — EIP-3009 authorization nonces are single-use at the CDP facilitator (source of truth for on-chain uniqueness). The gateway hardens four buyer/seller trust surfaces: payment-proof replay/race, SSRF on URL fetch, upstream bypass (shared-secret trust header), and Base congestion / settle-latency (pending + retry same proof — never treat HTTP timeout alone as “payment failed”).

What it is

A thin self-hosted tollgate in front of your API or MCP tools. When an agent calls a paid route, it gets HTTP 402 as a price tag (not a hard deny). It pays a small USDC (or configured USDT) amount; you deliver. Default clearing is Base + USDC via Coinbase CDP; multi-network accepts are env-driven (see matrix below). Humans can still hit a free path; agents convert at the booth.

Self-host is free (MIT). Repo: github.com/kevin2003050666-coder/x402-micro-tollgate · Questions: 2767111713@qq.com

Not an official Coinbase product. Not a full agent marketplace. Not a billing SaaS. A sharp Visa-style tollbooth. Not fiat custody.

Why this exists: MANIFESTO.md — pain, engineering, on-chain proof, MIT.

Network × asset matrix

Default deploy profile: Base USDC only (dev: Base Sepolia). Enable multi with NETWORKS + ASSETS or ACCEPTS_JSON / X402_* aliases. Browser HTML 402 shows a chain + asset picker when more than one accept is configured.

USDT on EVM typically uses extra.assetTransferMethod: "permit2" (not EIP-3009). FeeSplitter production path remains Base + USDC; other chains are config stubs under contracts/deployments/.

Browser wallets

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Who it’s for

• API sellers who want agents to pay per call — without building a billing console or selling monthly seats
• Tool builders shipping paid MCP endpoints into Cursor / Claude
• Operators who want Visa-like take-rate economics (0.1%), not hosting invoices

How money works

1. Price tag — unpaid traffic gets HTTP 402 with the amount due (conversion, not rejection)
2. Pay — the agent settles a USDC micropayment in seconds via Coinbase CDP
3. Unlock — the tollgate proxies to your upstream; you keep ~99.9%, protocol take 0.1%

No protocol monthly fee. Monetization is the toll — like interchange on card rails.

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1-minute quickstart

Requires Node.js 22+.

git clone https://github.com/kevin2003050666-coder/x402-micro-tollgate

cd x402-micro-tollgate && cp .env.example .env

set CDP_API_KEY_ID, CDP_API_KEY_SECRET, X402_PAY_TO (optional: PUBLIC_BASE_URL, UPSTREAM_URL)

npm i && npm start

curl http://127.0.0.1:8402/health → 200

curl http://127.0.0.1:8402/x402/discover → 200 (free agent yellow pages)

curl http://127.0.0.1:8402/v1/quote → 402

curl "http://127.0.0.1:8402/v1/fetch-md?url=https://example.com" → 402 (paid HTML→Markdown demo)

npx one-liners (no clone):

npx x402-micro-tollgate@0.3.3

npx x402-micro-tollgate@0.3.3 --seller 0xYourReceivingAddress --stdio

--seller / -s sets X402_PAY_TO before boot (env vars still work). Default without --stdio is HTTP + /mcp on port 8402.

Agent / crawler docs: llms.txt (also GET /llms.txt and GET /.well-known/llms.txt) · OpenAPI 3.1: docs/openapi.yaml · well-known: GET /.well-known/x402.json, GET /.well-known/agent-card.json

Alternative one-liner: docker compose up --build

Without CDP keys the process runs in demo mode (protocol-shaped 402 / MCP PaymentRequired, no on-chain settle).

Cursor mcp.json:

{

"mcpServers": { "x402-micro-tollgate": { "url": "http://127.0.0.1:8402/mcp" } } }

Stdio:

{

"mcpServers": { "x402-micro-tollgate": { "command": "npx", "args": [ "x402-micro-tollgate@0.3.3", "--seller", "0xYourReceivingAddress", "--stdio" ], "env": { "CDP_API_KEY_ID": "...", "CDP_API_KEY_SECRET": "...", "PUBLIC_BASE_URL": "https://your.public.host" } } } }

(X402_PAY_TO in env still works if you omit --seller.)

Library drop-in (permissionless seller)

import express from "express";

import { x402Tollgate } from "x402-micro-tollgate";

const app = express(); app.use("/v1", await x402Tollgate({ seller: process.env.SELLER! }));

Or set SELLER / X402_SELLER in .env and run npm start. See Environment for the $10 threshold, factory address, and fee-release details.

Buyer / Agent client

Thin TypeScript helper that wraps official @x402/fetch + @x402/evm ExactEvmScheme. On HTTP 402 it parses PAYMENT-REQUIRED, checks budgets, signs EIP-3009 once, and retries once with PAYMENT-SIGNATURE (never loops).

npm i x402-micro-tollgate@0.3.3

import { createX402Fetch } from "x402-micro-tollgate/client";

const fetch402 = createX402Fetch({ privateKey: process.env.BUYER_KEY as 0x${string} }); const res = await fetch402("https://x402-micro-tollgate.onrender.com/v1/quote");

Defaults: maxSingleSpendUsdc = 0.05, maxTotalSpendUsdc = 1.00 (clear Error if exceeded). Circuit breaker (before sign): max 10 paid 402s / 0.05 USDC per rolling 60s, plus fingerprint dead-loop halt (maxPaidRequestsPerMinute, maxSpendUsdcPerMinute, enableFingerprintBreaker). Hot-wallet warning: keep only ~$5–$10 USDC on the signing key — treat it as an agent spend faucet, not a treasury.

Human-delegated agent credit (CLI)

Thin PoC: Human sets `B_max` → Agent loops createX402Fetch against a paid URL (auto 402 → pay once → retry). Chrome / Telegram / Session Key / Passkey UI are deferred.

# SAFETY: fund BUYER_PRIVATE_KEY with ≤ $5–$10 USDC only. Never commit keys.

export BUYER_PRIVATE_KEY=0xYourHotWalletKey

optional: TARGET_URL MAX_SINGLE_USDC MAX_TOTAL_USDC ROUNDS

npm run poc:buyer-agent

or: npx tsx scripts/buyer-agent-poc.ts

The script imports the local client (../src/client) so repo CI does not need a live chain pay. For a live demo against the published package, swap the import to x402-micro-tollgate/client (same API as 0.3.2+). Each round prints status, autoPaid, and sessionSpendUsdc on stdout; the safety banner goes to stderr.

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Deploy

Uses render.yaml: Node 22, npm start, health /health, env names from .env.example. Set CDP_API_KEY_ID, CDP_API_KEY_SECRET, and X402_PAY_TO in the dashboard for live settlement; set PUBLIC_BASE_URL to your https://….onrender.com origin for Bazaar.

Ops bump: redeploy discover + well-known (force Render GitHub auto-deploy so production picks up GET /x402/discover, GET /.well-known/x402.json, GET /.well-known/agent-card.json, and MCP fetch_md). If auto-deploy does not fire within a few minutes after this lands on main, use the Render dashboard → Manual Deploy → Deploy latest commit.

Self-host production: Docker — docker compose up --build (see Dockerfile / docker-compose.yml).

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Environment

| X402_MIN_PRICE_USDC | — | Optional static minimum accept amount (atomic USDC). Effect