---
title: "Check an x402 seller before you pay: wallet, domain, sanctions"
method: POST
path: "/v1/seller/preflight"
---

# Check an x402 seller before you pay: wallet, domain, sanctions

`POST /v1/seller/preflight`

## Request

- Base URL: `https://api.limitguard.ai`
- URL: `https://api.limitguard.ai/v1/seller/preflight`
- Auth: one of:
  - API key in header `X-API-Key`
  - none

Preflight before an agent pays an x402 seller: screens the payTo wallet against the OFAC SDN address list, reads who registered the resource domain and when (RDAP), and screens that company against the OFAC, EU and UN lists. Compares the payTo with the wallet the seller publishes in its 402 and /.well-known/x402, and blocks a lookalike (address poisoning). Returns ok, caution or block with one reason per finding.

## Request body

- object
  - `pay_to` string, required: The payTo wallet of the x402 quote you are about to pay
  - `network` string: CAIP-2 network of the quote (default eip155:8453); eip155:* or solana:*
  - `resource_url` string, required: The https URL of the paid resource, on a public DNS name
  - `payer` string: Optional: your own paying wallet (EVM). Its previous USDC payees on Base are compared with pay_to

## Response `200`

Success

## Other responses

- `402`: Payment required. The x402 v2 challenge is in the base64 PAYMENT-REQUIRED header and the JSON body; pay and retry with PAYMENT-SIGNATURE, or send X-API-Key with prepaid balance.

---

[API](https://skmtc.dev/limitguard/apis/limitguard-ai.md) · [All operations](https://skmtc.dev/limitguard/apis/limitguard-ai/llms.txt) · [OpenAPI document](https://skmtc.dev/limitguard/apis/limitguard-ai/revisions/8f9718bce4a1?raw)