TollGate

The payment rails the agent economy runs on. HTTP 402 for autonomous payments + AgentScore credit reputation, bound to ERC-8004 identity. 18 contracts across 5 chains.

Live demo · API server · 0G mainnet contract · GitHub

Turn any API, data feed, inference job, or storage write into a paid AI-agent service using HTTP 402 Payment Required, stablecoin settlement, on-chain agent budgets, and verifiable receipts — no accounts, no API keys, no human approval loop.

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The problem

AI agents will execute over $10 trillion in autonomous economic decisions by 2030. Today they have zero native payment infrastructure: no service discovery, no per-request billing, no spending limits, no proof of delivery, no credit history. Every agent still relies on human-in-the-loop approval to pay an API.

HTTP 402 Payment Required was reserved in the HTTP spec for exactly this case in 1997. TollGate makes it real for the agentic era — fully on-chain, replay-safe, and chain-agnostic.

The solution

A single gateway that agents talk to over standard HTTP. The gateway issues a payment challenge, the agent settles USDC on-chain, and the response unlocks. Every call produces a cryptographic receipt anchored to a blockchain, an on-chain audit trail in AgentReceiptRegistry, and an ERC-721 NFT. Agents accumulate an on-chain credit score (AgentCreditRegistry) from their receipt history — just like a FICO score, but for AI.

Key features

Feature	Description
x402 payment gateway	HTTP 402 challenges: single-use, replay-safe, SHA-256 request-hash bound, 5-min expiry
Multi-chain	0G · Mantle · Arbitrum · Base · QIE · Sui · Polygon — one unified gateway
On-chain budget enforcement	AgentBudgetController: smart-contract daily caps + per-request limits
Agent credit score	AgentCreditRegistry: FICO-style score built from on-chain receipt history
Receipt NFTs	ERC-721 minted per payment, live in Economy Dashboard via SSE
MCP server (9 tools)	Claude Desktop agents call TollGate natively — pay_for_service, list_services, etc.
A2A auto-cycle	Agents hire each other autonomously every 5 s; decision logs anchored on-chain
SQLite receipt ledger	Receipts survive server restarts; queryable at GET /api/receipts

How x402 works

Agent → GET /api/gateway/svc_0g_inference
      ← 402 { challengeId, payTo, amount, network, requestHash, expiresAt }
      → pays USDC on-chain
      → retries with X-PAYMENT: <base64 proof>
      ← Gateway verifies: recipient · amount · network · challenge binding · replay check
      ← { data, receiptId } + SQLite write + SSE event + NFT mint

Architecture

Component	Path	Description
Frontend	src/	React 19 + Vite 7 + Tailwind v4. Workspace selector → per-workspace dashboard with live Economy Dashboard (SSE), paid-API tabs, Agents panel, and Receipts ledger.
Server	server/	Express + TypeScript. Real 402 gateway middleware, SQLite receipt ledger, SSE payment feed, and an MCP server exposing 9 tools so Claude Desktop agents call TollGate natively.
Contracts	contracts/	18 Hardhat-deployed Solidity contracts across 0G, Mantle, Arbitrum, QIE, and Arc.
SDK	packages/sdk/	@tollgate/sdk — zero-dependency x402 client: fetchPaid() + createTollGate().

Workspaces

Each workspace is a self-contained deployment with its own contracts, paid API services, UI tabs, and network configuration.

Workspace	Route	Networks	What it does
0G	/app/0g	0G Mainnet · Galileo Testnet	AI inference + decentralised storage economy; A2A agent loop; MCP server
Mantle	/app/mantle	Mantle Mainnet	Agent wallets with on-chain spend policies; mETH/USDY yield signals; agent credit scoring
Arbitrum	/app/arbitrum	Arbitrum Sepolia · One	USDC per-call services with escrowed delivery; Orbit chain monitoring
QIE	/app/qie	QIE Testnet	Merchant checkout rail; QIE Pass NFT gating; on-chain oracle feed
Sui	/app/sui	Sui Mainnet · Testnet	Agent Economy OS: DeepBook yield escrow, Walrus receipts, Seal encryption, Intent Engine
Agora	/app/agora	Arc Mainnet · Base	ArcMind autonomous trading: copy-trading, reasoning traces, kill switch
Polygon	/app/polygon	Polygon zkEVM	UAE commerce: AED invoice tokenisation, cross-border stablecoin remittance

Deployed contracts

0G Mainnet — chainId 16661

Contract	Address
AgentReceiptRegistry	0x801ddc5a54E5a7F1d0D6900AA996A04E26D0307f
AgentIdentityRegistry	0x8769E9ad02728d49D08CE2F5D5cd4ce75EeC0446
ServiceRegistry	0x2b27425bd22Ae883dEc34F7a8Eacacf336C562b8
AgentBudgetController	0x305eF265BD964fBe34913E70Ef6AA8951e6b662e
DeliveryVerifier	0x5F4999829D57f714497343f5677e66e6A56238E3

Mantle Mainnet — chainId 5000

Contract	Address
AgentIdentityRegistry	0x4cA80A3af6e0a4E0c85AB31E3B4a86C6BffF17CB
AgentCreditRegistry	0xA8FdDb9F6f54Fbf127cb8c71049cB1e19f5836F9
AgentVault	0x801ddc5a54E5a7F1d0D6900AA996A04E26D0307f
AgentBudgetController	0x2b27425bd22Ae883dEc34F7a8Eacacf336C562b8
ReceiptNFT	0x5F4999829D57f714497343f5677e66e6A56238E3

Arbitrum Sepolia — chainId 421614

Contract	Address
AgentEscrow	0x801ddc5a54E5a7F1d0D6900AA996A04E26D0307f

QIE Testnet — chainId 1983

Contract	Address
QieCheckout	0x801ddc5a54E5a7F1d0D6900AA996A04E26D0307f
QiePass	0x8769E9ad02728d49D08CE2F5D5cd4ce75EeC0446

Arc Testnet — chainId 5042002

Contract	Address
ArcMindRegistry	0x24Cb6d1bE131006e8CB2cb7fBa5675725f9E6Da8

Quick start

# Frontend
npm install
npm run dev          # Vite on :5173

# Server
cd server
npm install
cp .env.example .env   # fill in keys
npm run dev          # Express on :8787

API reference

GET  /api/services              list all paid services (?workspace=0g)
GET  /api/services/:id          service details
GET  /api/agents                list agents (?workspace=)
GET  /api/agents/:id            agent details
GET  /api/v1/x402-spec          x402 discovery document
GET  /api/gateway/:serviceId    → 402 challenge or unlocked response
POST /api/gateway/:serviceId    same, for POST payloads
GET  /api/receipts              receipt ledger (?workspace=&service=&agent=)
GET  /api/receipts/:id          single receipt
GET  /api/receipts/stats        economy stats (total, today, agents, avg)
GET  /api/agent-score/:agentId  FICO-style credit score from receipt history
GET  /api/events/payments       SSE: live payment feed (snapshot + receipt + nft_update)
POST /api/og/upload             0G Storage upload (server-signed)
POST /api/og/compute            0G Compute inference (server-signed)
GET  /api/status/health         server health + version
GET  /api/status/activity       activity snapshot
POST /mcp                       MCP server (JSON-RPC 2.0, 9 tools)

SDK

import { fetchPaid, createTollGate } from "@tollgate/sdk";

const data = await fetchPaid("https://tollgate-1.onrender.com/api/gateway/svc_0g_inference", {
  proof: async (challenge) => myWallet.signAndPay(challenge),
  agentId: "my-agent",
});

MCP server (Claude Desktop)

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "tollgate": {
      "command": "npx",
      "args": ["-y", "@tollgate/mcp-bridge", "--url", "https://tollgate-1.onrender.com/mcp"]
    }
  }
}

Claude can then call list_services, pay_for_service, get_receipt, and 6 more tools natively.

Tech stack

Layer	Technology
Frontend	React 19, Vite 7, Tailwind CSS v4, TypeScript
Server	Node.js, Express, TypeScript, better-sqlite3, ethers v6
Contracts	Solidity 0.8, Hardhat, OpenZeppelin
Payments	HTTP 402 (x402 protocol), USDC ERC-20, ERC-721 NFT receipts
Storage	0G Storage (Merkle-root anchored), Walrus (Sui)
Identity	ERC-8004 agent identity, EIP-191 signatures
MCP	JSON-RPC 2.0 MCP server, Claude Desktop integration
Chains	0G · Mantle · Arbitrum · Base · QIE · Sui · Polygon zkEVM · Arc

Security

TollGate handles real on-chain payments.

Server hardening:

• HTTP security headers (X-Frame-Options: DENY, X-Content-Type-Options: nosniff, Referrer-Policy) on every response. Mirrored in vercel.json.
• Rate limiting: /api/og/upload 10 req/min, /api/gateway/:id 30 req/min/IP, /mcp 60 req/min.
• X-Agent-Id truncated to 128 printable-ASCII chars to prevent log injection.
• X-Request-Id validated against [a-zA-Z0-9_-]{1,64}.
• x402 challenges are single-use, expire in 5 minutes, and are bound to a SHA-256 request hash.
• 500 responses return { error: "internal_error" } only — no stack traces.
• Model inference endpoint has an allowlist — unknown model IDs return 400.

Frontend hardening:

• All user-entered amounts pass through safeAmt() — NaN, negative, and overflow values rejected before any on-chain call.
• Tx hash links rendered only after isTxHash() validates the 64-char hex — prevents open-redirect.
• Ethereum addresses validated with /^0x[0-9a-fA-F]{40}$/ before any transaction.

Known limitations:

• CORS_ORIGIN=* by default; tighten to your domain before production.
• MCP create_service accepts arbitrary endpoint URLs — add an SSRF blocklist before public deployment.

Full security policy: SECURITY.md

Testing

# Unit tests
npm test

# Integration / flow test (requires server running on :8787)
node scripts/test-flow.js

The flow test exercises the full x402 cycle: service discovery → 402 challenge → dev-bypass payment → receipt verification → agent credit score. All credentials are loaded from server/.env.