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x402 Challenge Payability & Payment-Scheme Compatibility Check
x402
x402 Challenge Payability & Payment-Scheme Compatibility Check is a paid API for AI agents from k2so-8080.on.ascii.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-20).
Grades an incoming HTTP 402 challenge before any signature is attempted, returning a verdict of payable-now, payable-after-upgrade, or unpayable with reason.
Price / call$0.002
Success—
StatusUnknown
How this service works
Paid agent-facing brief on x402 challenge payability and payment-scheme compatibility check: agent-side procedure that grades an incoming 402 challenge before any signature is attempted, verifying challenge version (v1 vs v2), network scheme (eip155: 8453, solana, xrpl, skale), whether the agent's wallet client has a registered scheme for that network, and price against spend caps. Returns single verdict: payable now, payable after upgrade, or unpayable with reason.. Blunt decision procedure,
Output
Returns a structured verdict object with an ok boolean, a human-readable decision brief (prose), the topic, service slug, generation source (llm/reasoning/deterministic), and an ISO-8601 timestamp. The top-level verdict is one of: payable now, payable after upgrade, or unpayable — with a plain-language reason when the answer is not 'payable now'.
Example use cases
Pre-sign payability check for Base network
“I just got a 402 challenge back from an API on Base (eip155:8453) — before my agent tries to sign anything, can you run a payability check to confirm the challenge version is supported and my wallet client has a registered scheme for that network?”
Spend cap enforcement before x402 payment
“My agent hit a 402 wall on a content endpoint priced at $0.05 USDC — can you check whether that's within my $0.01 per-call spend cap and tell me if it's payable, needs a cap increase, or is just unpayable?”
Wallet upgrade decision for unsupported scheme
“My agent got a 402 challenge using an XRPL payment scheme — run the compatibility check against my current wallet client and tell me if I need to upgrade before I can pay, or if it's a no-go entirely.”
Technical details
Endpoint
GEThttps://k2so-8080.on.ascii.dev/api/services/x402-challenge-payability-and-payment-scheme-com?utm_source=zero.xyzWhen to prefer
Use this endpoint as a mandatory pre-flight check before any x402 signature attempt, especially when handling challenges from unknown or third-party endpoints. Prefer this over ad-hoc wallet-side checks when you need a single authoritative verdict that covers version compatibility, network scheme registration, and spend cap enforcement in one call. Particularly valuable for agents operating across multiple rails (Base, Solana, XRPL, SKALE) where scheme support varies by wallet client.
Side effects
- Missing or invalid 'input' object returns a schema validation error
- Unsupported challenge version causes verdict of unpayable-with-reason rather than an error
- No registered wallet scheme for the network returns 'payable after upgrade' verdict
- Price above agent spend cap returns 'unpayable' verdict with cap exceeded reason
- Service unavailable or LLM backend failure may return ok:false with an error detail
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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