# x402 Payment Challenge & Payload Conformance Linter

> x402 Payment Challenge & Payload Conformance Linter is a paid API for AI agents from agents.daedalusdevelopmentgroup.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-20).

Statically validates x402 v2 payment challenges and signed paymentPayload objects against the full protocol spec, returning a signed verdict with exact per-failure remediations — no network fetch required.

## Facts

- Endpoint: POST https://agents.daedalusdevelopmentgroup.com/v1/x402/402-lint?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-payment-challenge-payload-conformance-linter-9f59dccc
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_B1KnZXy81AKILMiDfs-Bh

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-payment-challenge-payload-conformance-linter-9f59dccc -d '<json body>'
```

Example prompt: Can you lint this x402 v2 payment challenge for me and tell me exactly what's wrong with it? Here's the payload — I need to know if the accepts scheme, payTo address, EIP-712 metadata, and PAYMENT-REQUIRED header all conform to spec, and if not, what exactly to fix.

## When to prefer this

Choose this endpoint when you need a fast, offline, static conformance check of an x402 v2 payment challenge or signed paymentPayload without making any network requests. It is ideal for pre-deployment validation, CI/CD lint steps, or debugging rejected payments when you need exact per-field remediations rather than a generic error. Prefer it over manual spec-reading or live facilitator round-trips when you need deterministic, signed verdicts you can act on immediately.

## Known failure modes

- Missing required fields in the 402 challenge object returns specific field-level errors
- Invalid or unsupported accepts scheme/network/asset combination flagged as non-conformant
- EIP-712 metadata shape mismatch returned with remediation
- Header-version mismatch between PAYMENT-REQUIRED header and payload body flagged explicitly
- Expired or missing nonce/expiry in paymentPayload returned as authorization failure
- Malformed resource URL or description exceeding cliff limits returned with remediation
- Bazaar extension shape violations returned as separate failure entries
- Request body missing required 'input' or 'output' wrapper returns 400-level error

## How this service works

Static conformance lint of an x402 v2 402 challenge and/or a signed paymentPayload: version, resource URL/description cliff, accepts scheme/network/asset/atomic-amount/timeout/payTo, EIP-712 token metadata, bazaar extension shape, PAYMENT-REQUIRED header decodability, header-version mismatch, and payload authorization/nonce/expiry. Returns a signed conformant verdict with an exact remediation per failure. No network fetch.

## Output

A signed conformance verdict indicating whether the submitted x402 challenge and/or paymentPayload passes validation, plus a structured list of every failure with an exact, field-level remediation instruction for each. No network calls are made; all checks are purely static.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input",
  "output"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object"
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST",
      "PUT",
      "PATCH"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": true
  },
  "output": {
   "type": "object",
   "required": [
    "type",
    "example"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "ok": true
    }
   },
   "additionalProperties": true
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-payment-challenge-payload-conformance-linter-9f59dccc/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agents.daedalusdevelopmentgroup.com](https://www.zero.xyz/host/agents.daedalusdevelopmentgroup.com/llms.txt)