# x402 Endpoint Preflight

> x402 Endpoint Preflight is a paid API for AI agents from api.zfinia.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-18).

Probes an x402-enabled endpoint to reveal its payment requirements (price, network, asset, payTo address) and declared schemas without sending any payment.

## Facts

- Endpoint: POST https://api.zfinia.com/x402/v1/x402-endpoint-preflight?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-18
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-endpoint-preflight-b3a529dc
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_W4sl0gs3iAnqnHijTWVNG

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-endpoint-preflight-b3a529dc -d '<json body>'
```

Example prompt: Before I pay anything, can you check what this x402 endpoint at https://api.example.com/some-resource will charge me — I want to know the price, which network and asset it uses, and the payTo address?

## When to prefer this

Use this endpoint when an agent or developer needs to inspect an x402-gated endpoint's payment requirements and schemas before committing any funds. It is the right choice when you want to validate cost, asset type, network, and API shape without side effects. Prefer it over the x402 Challenge Decoder when you don't already have the raw 402 response body — this endpoint performs the probe itself.

## Known failure modes

- URL is not on a reviewed origin — request refused
- URL contains credentials, ports, or fragments — request refused
- Endpoint does not return a 402 response — no challenge to decode
- Redirect encountered — refused rather than followed
- Malformed or missing x402 challenge header/body — decoding fails
- Endpoint unreachable or times out

## How this service works

Find out what an x402 endpoint will charge before you pay it. Probes the endpoint, reads the challenge from the header or the body, and returns the decoded price, network, asset and payTo plus the declared input and output schemas. Never sends a payment. Only reviewed origins are reachable, and a redirect is refused rather than followed.

## Output

Returns the decoded x402 payment challenge including the required price, network name, asset (e.g. USDC), payTo address, and the endpoint's declared input and output JSON schemas. No payment is made or initiated.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "maxLength": 2048
  },
  "body": {
   "type": "object"
  },
  "method": {
   "enum": [
    "GET",
    "POST"
   ],
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-endpoint-preflight-b3a529dc/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.zfinia.com](https://www.zero.xyz/host/api.zfinia.com/llms.txt)