# x402check agent docs

Paid per tool. No free checks. Unit **$0.002** USDC Exact on Base (eip155:8453).

## Single

```
GET https://x402check.dev/preflight?url=https%3A%2F%2Fwww.api-xpay.com%2Fx402%2Fping
```

## Batch (N × $0.002 in one Exact payment)

```
POST https://x402check.dev/preflight
{"urls":["https://a.example/x402","https://b.example/x402"]}
```

Limitation: x402 Exact = one settlement per HTTP request. Batch uses DynamicPrice = N×unit, not N separate txs.

## Adopt by default

- Client wrapper that calls preflight before any x402 pay (`x402check-client`)
- Runtime skill/middleware default-on with env kill-switch
- Policy: avoid→deny, caution→confirm, ok→still enforce maxAmount
- Bazaar listing + OpenAPI + MCP descriptor
- Keep p95 <300ms via cache so agents don't skip

## When to use (prompt coverage)

- Before paying any x402 endpoint / before signing USDC on Base
- Is this x402 endpoint safe / legit / a scam?
- Verify payTo; detect payTo or price changes
- Uptime / is the endpoint down
- Compare tools; pick cheapest or most reliable
- Budget guard; audit log of payment decisions
- Validate 402 payment requirements; debug failing settles

## MCP tools

preflight_check · verify_payto · preflight_batch · compare_tools (aliases share per-URL billing)

## Machine-readable

- [openapi.json](https://x402check.dev/openapi.json)
- [llms.txt](https://x402check.dev/llms.txt)
- [llms-full.txt](https://x402check.dev/llms-full.txt)
- [mcp.json](https://x402check.dev/mcp.json)
- [mcp/server-card](https://x402check.dev/mcp/server-card)