GuardX402 — Stop Runaway Agent Spend

GuardX402

Documentation

The policy and audit layer for AI agents making x402 payments.

OWS handles

🔑 Secure private key storage
✍️ Transaction signing
🌐 9 chains supported
🏦 Wallet creation & management

GuardX402 handles

📋 Spend policy enforcement
💰 Budget tracking & alerts
📝 Tamper-evident audit logs
👥 Team access controls

Payment flow

Agent→POST /api/guard/check→Policy Engine

Approved→OWS Signs→x402 Payment

Blocked→Agent Stops

Quick Start

Up and running in under 5 minutes.

Sign up at guardx402.com

Create a free account, register your first agent, and copy your API key from the dashboard.

Install OWS (recommended)

npm install @open-wallet-standard/core

Add to your agent

TypeScript + OWS

import { createWallet, signMessage } from '@open-wallet-standard/core';
const wallet = createWallet('my-agent');

const check = await fetch('https://guardx402.com/api/guard/check', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'x-api-key': 'ng_your_key_here'
  },
  body: JSON.stringify({
    endpoint: 'https://api.perplexity.ai/chat',
    amount: 0.002,
    chain: 'BASE',
    owsSigned: true
  })
});
const { approved, auditId } = await check.json();
if (!approved) throw new Error('Blocked');
// OWS signs the payment
const sig = await signMessage(wallet, 'evm', canonicalMessage);
await fetch('https://guardx402.com/api/guard/confirm', {
  method: 'POST',
  headers: { 'x-api-key': 'ng_your_key_here' },
  body: JSON.stringify({ auditId, txHash: sig, owsSigned: true })
});

POST

/api/guard/check

Check a payment against policy before executing. Call before every x402 payment.

Required header: x-api-key: ng_your_key_here

Request body

{
  "endpoint": "https://api.perplexity.ai/chat",
  "amount": 0.002,
  "chain": "SOL",
  "owsSigned": true
}

Field	Type	Description
endpoint	string	Full URL being paid
amount	number	USDC amount from 402 response
chain	SOL \| BASE	Chain for payment
owsSigned	boolean	Whether OWS will handle signing

Response

{
  "approved": true,
  "agentId": "agent-abc123",
  "budgetRemaining": 4.998,
  "budgetLimit": 5.00,
  "auditId": "audit-xyz789",
  "owsSigned": true,
  "owsSignature": "255880b9a220139a..."
}

Block reasons

reason	Description
budget_exceeded	Would exceed daily/weekly/monthly USDC limit
per_call_max	Single call exceeds per-call maximum
domain_blocked	Domain not in allowed list (Pro)
velocity_exceeded	Too many calls per hour (Pro)
agent_paused	Agent paused by team owner

POST

/api/guard/confirm

Log the on-chain transaction hash after payment settles. Always call this to complete the audit record.

Request body

{
  "auditId": "audit-xyz789",
  "txHash": "0xabc123...",
  "owsSigned": true
}

Response

{ "success": true, "auditId": "audit-xyz789" }

Policy Options

Configure per-agent spend policies from the dashboard or via the policy API.

Setting	Free	Premium	Pro	Description
Budget limit	✅	✅	✅	Max USDC per period
Per-call max	✅	✅	✅	Max USDC per payment
Alert threshold	✅	✅	✅	% of budget to trigger alert
Webhook alerts	❌	✅	✅	POST alerts to your endpoint (Premium+)
CSV export	❌	✅	✅	Download audit log as CSV (Premium+)
Velocity controls	❌	❌	✅	Max calls per hour (Pro)
Domain allowlist	❌	❌	✅	Only pay approved domains (Pro)

Built on Open Wallet Standard

GuardX402 is built on the Open Wallet Standard by MoonPay. OWS handles the wallet; GuardX402 handles the rules.

OWS role

🔐 Encrypted key storage at ~/.ows/
✍️ Signs transactions — private keys never leave the device
🌐 Supports 9 chains including Solana and Base
📦 Simple SDK: createWallet, signMessage

GuardX402 role

📋 Policy enforcement before every payment
💰 Budget tracking in real time
🔔 Alert your team at threshold
📊 90-day tamper-evident audit log (Pro)

Wallet setup

import { createWallet } from '@open-wallet-standard/core';
// Encrypted at ~/.ows/ — keys never in env vars or code
const wallet = createWallet('my-agent-name');
// EVM (Base): 0xb6E4641B6deCd8D8133C74DA00D5C021d4Bd8Da7
// Solana:     8HG7kQEsb28LW4ngRZTdmenHWfJfTGPT5Lfzc5RY6cHe

Learn more at openwallet.sh →

Frameworks

GuardX402 works with any agent framework — just HTTP POST.

Open Wallet Standard

OWS

Native OWS signing. Keys encrypted at rest.

npm install @open-wallet-standard/core

LangChain

Python

Add as a @tool in any LangChain agent.

pip install langchain requests

CrewAI

Python

Wrap as a BaseTool in any CrewAI crew.

pip install crewai

AutoGen

Python

pip install pyautogen

Custom REST

Any

Any language that can send an HTTP POST request.

curl -X POST https://guardx402.com/api/guard/check \

Plans

Start free. Upgrade when you need more.

Free

$0/mo

✓ 1 agent
✓ 1 team seat
✓ 5,000 checks/mo
✓ 7-day audit history
✓ Budget & per-call limits
✗ Webhook alerts
✗ CSV export

Get Started Free

About

"The agentic economy needs guardrails. GuardX402 is the policy layer that makes AI agent payments safe for everyone — from solo developers to enterprise teams."

Luana Cantu

📍 Miami, FL

Lead Architect · Full-Stack Developer · Developer Advocate

Founder of NodusAI — AI-powered prediction market research oracle. Builder at the intersection of AI, Web3, and SaaS. Previously CMO at KOKODI Games, Creative Director at Flying Rhino Web3 Marketing Agency across 5 regions. Inaugural subject of Avalanche's Proof of Thought #001.

𝕏 @luacantu GitHub @luacantu luacantu.com nodusai.xyz

Our Mission

AI agents are moving real money — autonomously, without guardrails. GuardX402 exists to make sure every x402 payment an AI agent makes is intentional, authorized, and audited. We believe the agentic economy needs the same financial controls that humans take for granted — budgets, limits, audit trails, and the ability to say no.

Built for the OWS Hackathon

GuardX402 was built for the Open Wallet Standard Hackathon — three rounds of building on the OWS protocol by MoonPay. The hackathon challenged builders to create real products on top of OWS, the open-source standard that gives AI agents a secure, universal way to hold value and sign transactions.

hackathon.openwallet.sh →

Build timeline

Morning

Concept + architecture + database schema

Afternoon

Core guard check API + Redis + OWS integration

Evening

Dashboard + Crossmint auth + onboarding flow

Night

Docs + GitHub + guardx402.com live

Media Kit

Brand assets, colors, and boilerplate for press and integrations.

Brand name

✓ CorrectGuardX402

✗ WrongGuard X402 · guardx402 · Guard x402

Tagline

Stop Runaway Agent Spend.

One-liner

GuardX402 is the policy and audit layer for AI agents making x402 payments on Solana and Base. Built on the Open Wallet Standard.

Logo assets

Logo variant 1

Logo variant 2

Brand colors

Brand Blue

#3d88d9

Dark Navy

#1a2744

Shield Steel

#6b9fd4

Energy Violet

#7C3AED

Cloud Lavender

#c8d8f0

Spark White

#ffffff

Background

#F8F9FB

Dark Text

#0F172A

Key facts

Protocolx402

ChainsSolana + Base

SettlementUSDC

Response timeunder 200ms

Wallet standardOWS v1.2.4

LicenseMIT open source

LaunchedApril 2026

Built inMiami, FL

Boilerplate

GuardX402 is an open-source x402 spend control platform for AI agents. Built on the Open Wallet Standard (OWS) by MoonPay, GuardX402 enforces budget policies, blocks overspend, and provides real-time audit logs for every x402 payment on Solana and Base. Free plan available. Premium at $15/mo. Pro plan at $35/mo. Live at guardx402.com.

Press contact:
X: @luacantu
GitHub: github.com/luacantu/guardx402
Built by: Luana Cantu · luacantu.com