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Pay Guard – x402 Pre-Payment Safety Check
x402
Pay Guard – x402 Pre-Payment Safety Check is a paid API for AI agents from seenly-pay-guard.vercel.app, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-22).
Validates a planned x402 micropayment before execution by checking wallet-domain trust, price limits, asset/network correctness, URL safety, lookalike domains, and wash-trading flags.
Price / call$0.01
Success—
StatusUnknown
How this service works
Score JSON, code, scrapes and LLM output for quality before your agent uses it: broken JSON auto-repair, schema checks, blocked-scrape and refusal detection. $0.03 per check via x402.
Output
Returns a verdict of allow, warn, or block along with detailed sub-checks: whether the wallet address is verified for the seller domain, whether the requested amount stays within the agent's price cap, whether the asset and network match expectations, whether the resource URL or domain shows lookalike/phishing signals, and whether wash-trading flags have been raised by Agentropolis.
Example use cases
Block overprice attack on agent
“My AI agent just received a 402 response from data-feeds.io asking for $2.00 USDC on Base — but I told it never to pay more than $0.10. Run it through Pay Guard and block the payment if the price exceeds my cap.”
Lookalike domain phishing screen
“Before my agent pays the x402 challenge from 'coinbaise.com' (payTo 0xDEF...456, 1000 USDC atomic units, Base network), check Pay Guard to see if that domain is a lookalike or known phishing site.”
Wallet-domain trust verification
“I want to make sure the wallet address 0x789...ABC in this 402 challenge is actually verified for the domain seenly.io before my agent sends any USDC on Base — can Pay Guard confirm that?”
Technical details
Endpoint
GEThttps://seenly-pay-guard.vercel.app/api/guard?utm_source=zero.xyzWhen to prefer
Use Pay Guard when your AI agent is about to execute an x402 micropayment and you need a fast, deterministic, non-LLM safety layer that combines domain trust, price enforcement, network validation, and phishing/wash-trade detection in a single call. Prefer this over manual checks or generic URL scanners when operating in the x402 protocol ecosystem specifically, where the 402 challenge structure (payTo, amount, asset, network, resource) is the native input format.
Side effects
- Missing required challenge.payTo or amount fields returns a validation error
- Domain not found or unverifiable results in a warn or block verdict with a domain-check failure reason
- Amount exceeds max_price_usd cap triggers a block verdict
- Network or asset mismatch returns a warn or block with asset/network mismatch reason
- Invalid atomic unit format for amount may cause parsing errors
- Agentropolis wash-flag service unavailable may degrade wash-check sub-result
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| asset | string | |
| payTo | string | Shortcut: challenge.payTo at top level. |
| amount | string | |
| domain | string | Planned seller domain / host the agent intends to pay. |
| network | string | |
| challenge | object | The x402 402 challenge / accept entry the agent received. |
| requestKey | string | |
| max_price_usd | number | Hard cap the agent will not exceed (USD). |
| listed_price_usd | number | Optional expected listed price from the agent’s plan. |
Output
Schema · Response
{
"type": "json",
"example": {
"kit": "seenly.pay-guard",
"advice": "Safe to sign this 402 challenge under the stated plan.",
"checks": {
"wash": {
"id": "wash",
"status": "pass",
"summary": "No wash flags; payment evidence present."
},
"price": {
"id": "price",
"status": "pass",
"summary": "Challenge price $0.03 ≤ max $0.05."
},
"lookalike": {
"id": "lookalike",
"status": "pass",
"summary": "Resource host matches planned domain."
},
"url_safety": {
"id": "url_safety",
"status": "pass",
"summary": "Resource URL is https, no credentials, no IP literal."
},
"listed_price": {
"id": "listed_price",
"status": "pass",
"summary": "Challenge price within listed range."
},
"asset_network": {
"id": "asset_network",
"status": "pass",
"summary": "Asset/network OK (USDC on eip155:8453)."
},
"wallet_domain": {
"id": "wallet_domain",
"status": "pass",
"summary": "payTo matches the domain’s verified Agentropolis wallet."
}
},
"reasons": [],
"verdict": "allow",
"coverage": {
"notes": [],
"agentropolis": "full"
},
"check_version": "pay-guard-0.1.0"
}
}Tags
x402
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