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x402 Endpoint Preflight
x402
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.
Price / call$0.004
Success—
StatusUnknown
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.
Example use cases
Vetting an unknown x402 API cost
“I found this x402 endpoint at https://api.acmecorp.com/data/report — can you tell me what it will charge, what asset it wants, and what network it runs on before I decide whether to call it?”
Verifying schema before agent integration
“I'm about to integrate https://api.partner.io/analyze into my agent — can you probe it with a POST and show me its declared input and output schemas along with the payment details so I know what to send and what I'll get back?”
Comparing costs of multiple x402 endpoints
“I want to compare what these two x402 endpoints charge: first check https://api.serviceA.com/generate, then https://api.serviceB.com/generate — give me the price, asset, and payTo for each so I can pick the cheaper one.”
Technical details
Endpoint
POSThttps://api.zfinia.com/x402/v1/x402-endpoint-preflight?utm_source=zero.xyzWhen to prefer
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.
Side effects
- 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
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | |
| body | object | |
| method | string |
Tags
x402
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