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Overwing Preflight for x402
x402
Overwing Preflight for x402 is a paid API for AI agents from overwing.ai, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-14).
Evaluates an x402 payment-required challenge against an agent's spending policy and the x402 payee directory, returning allow/review/refuse with detailed reasons.
Price / call$0.002
Success—
StatusUnknown
How this service works
Overwing Preflight for x402: should an agent sign this payment? POST the PAYMENT-REQUIRED terms and your policy; get allow, review or refuse with reasons: terms vs policy, payee vs the x402 directory and the server's own manifest, price vs the record. $0.002 USDC, no account.
Output
A structured decision object containing one of: allow, review, or refuse; accompanied by specific reasons covering policy compliance (max per call, allowed networks, allowed/blocked payees, testnet flag, price drift), payee verification against the x402 directory and server manifest, and optionally a fresh-quote price comparison.
Example use cases
Guard agent from unexpected payee
“I got a payment-required response from an API I haven't used before. Check if the payee is in the x402 directory and whether the price is within my limit of $0.01 for new payees before I sign anything.”
Enforce per-call spending cap
“My agent is about to pay an x402 fee — run a preflight check on the payment terms and make sure it's under $0.05 per call and the payee matches what the server's manifest says.”
Verify price hasn't drifted
“Fetch the resource unpaid and compare the fresh quote against the payment-required terms I was given — I want to know if the price has drifted more than 25% before my agent pays.”
Technical details
Endpoint
GEThttps://overwing.ai/api/x402/preflight/x402?utm_source=zero.xyzWhen to prefer
Use this endpoint when an AI agent encounters an x402 PAYMENT-REQUIRED response and must decide whether to sign and forward payment before proceeding. It is specifically suited for x402 v2 protocol challenges and provides directory-backed payee verification that generic policy checks cannot offer. Prefer it over manual policy evaluation when you need cross-referencing against the x402 payee registry and server manifest in a single low-cost call ($0.002 USDC, no account required).
Side effects
- Malformed or undecodable PAYMENT-REQUIRED header returns a parsing error
- Unknown or unregistered payee returns a refuse with directory-miss reason
- Network not in allowed_networks list returns a refuse with network policy reason
- Price exceeds max_per_call_usd returns refuse with price policy reason
- Fresh quote fetch fails if requested_url is unreachable
- Policy object missing required fields may use defaults silently
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| policy | object | max_per_call_usd (default 0.05), new_payee_max_usd (0.01), allowed_networks, allowed_payees, blocked_payees, allow_testnets (false), max_price_drift (0.25) |
| network | string | The CAIP-2 network the agent would pay on, when the terms offer several |
| fresh_quote | boolean | Also fetch the resource unpaid and compare its quote with the terms given |
| requested_url | string | The URL the agent asked for; checked against the resource in the terms |
| payment_required | — | The PAYMENT-REQUIRED header value (base64 JSON) or the decoded x402 v2 object {x402Version, resource, accepts[]} |
Tags
x402
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