# x402check for sellers

> Watch your x402 endpoint so agents keep paying you. $5 Exact USDC buys 30 days of daily re-checks (prepaid, no auto-renew).

When your listing drifts from your live 402 challenge, your endpoint goes down, or your `payTo` changes, agents that call x402check may refuse to pay or choose another tool. Those are heuristics about the endpoint · not a legal accusation.

## Watch your endpoint ($5 / 30 days)

```
POST https://x402check.dev/watch
{"url":"https://yours.example/x402","webhookUrl":"https://hooks.example/x402check","email":"you@example.com"}
```

Pay $5 Exact USDC on Base (HTTP 402 → PAYMENT-SIGNATURE), or use MCP `watch_tool` with the same body and `params._meta["x402/payment"]`.

- Daily re-checks of one URL for 30 days
- Alerts via HTTPS webhook and/or email when payTo, price, network, or availability changes
- Status: GET https://x402check.dev/watch?id=…
- Renew: POST https://x402check.dev/watch/renew (another $5 for another 30 days; no auto-renew)

## Verify ownership & badge

1. Primary: sign a challenge with the endpoint's live payTo wallet (EIP-191 / ERC-1271)
2. Fallback: DNS TXT `x402check-verify=…` or `/.well-known/x402check-verify.txt`
3. Optional opt-in **Verified by x402check** badge (`/badge/<id>.svg`) when your latest private snapshot is pass

HTML: [sellers](https://x402check.dev/sellers) · [scan](https://x402check.dev/scan) · [owner](https://x402check.dev/owner)

## Agents still preflight

Buyers pay $0.01 for `GET /preflight?url=…`. Keeping your live challenge stable keeps you payable.