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X402 Payment Header Shape Validator
x402
X402 Payment Header Shape Validator is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-23).
Validates the shape and encoding of an x402 payment header, returning acceptance/rejection status, normalized evidence, and mismatch reasons.
Price / call$0.001
Success—
StatusUnknown
How this service works
X402 Payment Header Shape: X402 Payment Header Shape checks a caller-supplied payment header for bounded base64 or JSON shape from bounded caller-supplied values without an external provider. Call X402 Payment Header Shape 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 Payment Header Shape as vers…
Output
Returns contract-specific shape checks, normalized evidence extracted from the header, specific mismatch reasons if the header is malformed, and an explicit acceptance or rejection status indicating whether the x402 payment header is valid.
Example use cases
Pre-acceptance x402 header gate
“I'm about to fulfill a paid API request. Can you check this x402 payment header for me — here's the value: 'eyJwYXltZW50IjoidGVzdCJ9' — and tell me if the shape is valid or if there are any mismatches I should know about?”
Agent delivery pipeline guard
“Before my agent delivers a result to the caller, I need to verify the x402 payment header they sent is properly formed. Here's the header string: 'eyJjaGFsbGVuZ2UiOiJhYmMiLCJyZXN1bHQiOiJ4eXoifQ=='. Does it pass shape validation?”
Debugging a rejected payment header
“A client's payment keeps getting rejected and I'm not sure why. Can you run their x402 payment header through shape validation — the header value is 'eyJ0eXBlIjoieDQwMiIsInZlcnNpb24iOiIxIn0=' — and give me the specific mismatch reasons so I can debug it?”
Technical details
Endpoint
POSThttps://api.delx.ai/api/v1/x402/x402-payment-header-shape?utm_source=zero.xyzWhen to prefer
Use this endpoint when you need a fast, in-memory, offline shape check of an x402 payment header without calling any external payment provider. It is ideal as a pre-flight guard before accepting or fulfilling a paid request, especially in agentic pipelines where you need to reject malformed headers cheaply before committing to downstream work.
Side effects
- Header string exceeds 8192 character limit — returns an error or truncation rejection
- Header is neither valid base64 nor valid JSON — returns rejection with encoding mismatch reason
- Missing or empty header field — returns validation failure with missing-input reason
- Header passes shape but fails contract-specific checks — returns rejection with detailed mismatch reasons
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| header | string | Header supplied to X402 Payment Header Shape; used only for this bounded calculation and processed in memory without retention. |
Output
Schema · Response
{
"type": "json",
"example": {
"result": {
"encoding": "base64_json",
"shape_valid": true
},
"schema": "delx/util-x402-payment-header-shape/v1",
"status": "pass",
"evidence": {
"retained": false,
"input_sha256": "d2df40bf50f271956773fe4254a5de1a334515afca29fda6e60cd96f1ec08c63",
"external_calls": 0
},
"operation": "delivery_contract:x402_payment_header_shape"
}
}Tags
x402
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