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numberintel.dev x402 Preflight Attestation
x402
numberintel.dev x402 Preflight Attestation is a paid API for AI agents from numberintel.dev, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-02).
Checks whether a target x402-enabled HTTP endpoint is reachable, properly configured, and returns a quote for its payment requirements before committing to a paid call.
Price / call$0.02
Success—
StatusUnknown
How this service works
x402 conformance preflight of any endpoint: parses the 402 envelope, lints accepts[] (atomic units, payTo, network), reports the quote, Bazaar extension presence and problems. No purchase is made.
Output
Returns a JSON object with a grade (e.g. 'quote_ok'), the payment quote including USD price, payTo address, and network, whether the endpoint is reachable, the HTTP status code, x402 version, number of accepted payment options, whether a Base mainnet option exists, whether the Bazaar extension is present, and a list of any detected problems.
Example use cases
Pre-call payment quote check
“I want to call https://some-data-api.com/v1/records but I'm not sure how much it charges or if its x402 setup is valid — can you preflight that URL and tell me the USD price, payTo address, and network before I commit?”
Diagnosing a broken x402 endpoint
“My API at https://myservice.dev/v1/prices is supposed to accept x402 payments but clients are complaining it's not working — can you run a preflight attestation on it and tell me what problems it finds?”
Confirming Bazaar extension support
“Can you check https://thirdparty-api.io/v1/lookup and verify whether it has the Bazaar extension enabled and is on Base mainnet, and give me its x402 version and grade?”
Technical details
Endpoint
GEThttps://numberintel.dev/v1/attest/preflight?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need to validate or audit an x402-gated API before making a live paid call — especially to confirm price, payment address, network, and x402 protocol version without spending funds. Prefer it over blindly calling a pay-per-use endpoint when you want to surface configuration problems, confirm Bazaar extension support, or let a user review costs before authorizing payment.
Side effects
- Target URL unreachable — reachable: false with empty quote and non-empty problems list
- Target does not return HTTP 402 — grade reflects non-conformant status
- Malformed x402 response at target — problems list populated with parse errors
- Missing required query parameter 'target' — 400 Bad Request
- Payment not settled for this preflight call itself — 402 returned by the preflight endpoint
- Network timeout on target URL — reachable: false
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"grade": "quote_ok",
"quote": {
"usd": 0.01,
"payTo": "0x...",
"network": "eip155:8453"
},
"target": "https://api.example.com/v1/data",
"problems": [],
"reachable": true,
"http_status": 402,
"x402_version": 2,
"accepts_count": 1,
"base_mainnet_option": true,
"has_bazaar_extension": true
}
}Tags
x402
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