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X402 Challenge Shape Check
x402
X402 Challenge Shape Check is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-13).
Validates the required top-level fields and structure of a caller-supplied x402 payment challenge object, returning acceptance/rejection status and mismatch reasons.
Price / call$0.001
Success—
StatusUnknown
How this service works
X402 Challenge Shape Check: X402 Challenge Shape Check checks required top-level fields in a caller-supplied payment challenge from bounded caller-supplied values without an external provider. Call X402 Challenge Shape Check before paying for or accepting an x402 or agent delivery assembled from caller-supplied challenge and result metadata. Returns contract-specific checks, normalized evidence, mismatch reasons, and an explicit acceptance or rejection status for X402 Challenge Shape Check as v…
Output
Returns a structured result including: an explicit acceptance or rejection status for the challenge, contract-specific field checks, normalized evidence derived from the challenge, and a list of mismatch reasons explaining any structural problems found.
Example use cases
Pre-payment challenge gate for agent
“I have an x402 challenge object that just came in from a content paywall — before my agent pays it, can you check its shape and confirm all required fields are there, or flag any mismatches?”
Screening incoming agent delivery challenges
“My agent received a challenge as part of a delivery result. Before we accept it, validate the challenge structure and tell me whether it passes or should be rejected, including any mismatch reasons.”
Debugging a malformed x402 challenge
“This x402 challenge keeps getting rejected downstream and I'm not sure why — can you run a shape check on it and show me exactly which required fields are missing or wrong?”
Technical details
Endpoint
POSThttps://api.delx.ai/api/v1/x402/x402-challenge-shape-checkWhen to prefer
Use this endpoint when you need a fast, cheap ($0.001 USDC), stateless structural check on an x402 payment challenge before committing to paying or accepting it. Prefer this over manual field inspection when building agent pipelines that need to gate on challenge validity. It processes in memory without data retention, making it suitable for sensitive challenge objects.
Side effects
- Challenge object exceeds 128 properties limit, causing rejection
- Missing required top-level fields result in explicit rejection status with enumerated mismatch reasons
- Malformed JSON in the challenge object may cause a parsing error
- Empty challenge object returns rejection with all required fields listed as missing
- Network or service errors return HTTP 4xx/5xx without a validation result
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| challenge | object | Challenge supplied to X402 Challenge Shape Check; used only for this bounded calculation and processed in memory without retention. |
Output
Schema · Response
{
"type": "json",
"example": {
"result": {
"shape_valid": true,
"accept_count": 1,
"missing_fields": []
},
"schema": "delx/util-x402-challenge-shape-check/v1",
"status": "pass",
"evidence": {
"retained": false,
"input_sha256": "62072ab7fce77c19843d604f1566016ce4dbe3ea291d11d208433c905228eeab",
"external_calls": 0
},
"operation": "delivery_contract:x402_challenge_shape_check"
}
}Tags
x402
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