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Preflight Validation of Malformed 402 Payment Challenges
x402
Preflight Validation of Malformed 402 Payment Challenges is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-19).
Returns a blunt decision-procedure brief for agents to validate whether an incoming x402 payment challenge is well-formed before attempting payment
Price / call$0.002
Success—
StatusUnknown
How this service works
Low-cost decision procedure for agents that checks a 402 payment challenge before any payment attempt. Grades scheme version (registered network for the x402 version), price parseability, settlement deadline sanity, and required header completeness. Returns one verdict: approve, repair-and-retry, or refuse-with-evidence. Prevents wasted gas and failed settlements on malformed challenges.
Output
A JSON object containing a boolean ok status, a paid flag, and a result object with a human-readable 'brief' prose field containing the blunt decision procedure, plus the topic, service slug, ISO-8601 generatedAt timestamp, and generationSource (llm, reasoning, or deterministic). Also includes payment metadata such as payer address and transaction hash.
Example use cases
Guard rails before agent payment attempt
“I just received a 402 response from an API and I'm not sure if the challenge is valid — can you run a preflight validation check on it before I try to pay, so I don't waste funds on a broken challenge?”
Debugging malformed payment headers
“My agent keeps failing when it tries to pay a 402-gated endpoint — can you validate whether the 402 challenge itself is malformed and give me a blunt breakdown of what's wrong?”
Automated payment pipeline safety check
“Before my agent fleet processes any x402 payment challenge, I want them to always run a cheap preflight validation check first — can you set that up so they GET the validation brief and only proceed if it comes back as well-formed?”
Technical details
Endpoint
GEThttps://k2so.wrong.systems/api/services/low-cost-preflight-validation-of-malformed-402-p?utm_source=zero.xyzWhen to prefer
Choose this endpoint when an AI agent needs a cheap ($0.002 USDC), fast sanity-check on an x402 payment challenge before committing to an actual payment flow. It is ideal for agent pipelines that encounter 402-gated APIs frequently and need to screen out malformed or fraudulent challenges at low cost. Prefer this over attempting payment directly when you want to avoid wasting funds on broken challenges or when building defensive payment pipelines.
Side effects
- Missing required 'type' or 'method' fields in input returns a validation error
- Invalid HTTP method enum value (only GET, HEAD, DELETE accepted) causes rejection
- Network or service unavailability returns no response
- Malformed input schema causes 400-level error
- Payment verification failure if the $0.002 USDC micropayment is not properly settled via x402
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"paid": true,
"result": {
"ok": true,
"brief": "plain prose decision procedure (120+ words)",
"model": "deepseek/deepseek-v4-flash-0731",
"topic": "string topic",
"service": "low-cost-preflight-validation-of-malformed-402-p",
"procedure": "same as brief",
"generatedAt": "2026-01-01T00:00:00.000Z",
"generationSource": "deterministic"
},
"service": "low-cost-preflight-validation-of-malformed-402-p",
"provider": "K-2SO"
}
}Tags
x402
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