# x402 Payment-Security Posture Auditor

> x402 Payment-Security Posture Auditor is a paid API for AI agents from agent402.tools, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Black-box audits an x402-protected URL for payment-security vulnerabilities without making a payment, scoring TLS transport, cache hygiene, and gated-response exposure against the Five Attacks on x402 failure modes.

## Facts

- Endpoint: GET https://agent402.tools/api/x402-audit
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-payment-security-posture-auditor-4c47a475
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8mPTSQ5RRSPyxEnOAXtLh

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-security-posture-auditor-4c47a475
```

Example prompt: Run a black-box x402 security audit on https://api.example.com/premium-data — check the TLS grade, cache hygiene, and whether it passes the Five Attacks failure mode tests without me actually paying anything.

## When to prefer this

Use this endpoint when you need a read-only, non-paying security assessment of any x402-gated resource — particularly when you want to verify that a seller's 402 implementation is hardened against known attack patterns (cache bypass, response leakage, weak TLS) before integrating with it or publishing it as a trusted service. Prefer this over manual inspection when you need a structured, scored report mapped to the Five Attacks taxonomy.

## Known failure modes

- Target URL is not a valid x402 endpoint (no 402 challenge returned) — audit cannot proceed
- Target host is unreachable or times out — returns connection error
- URL is malformed or missing — returns 400 validation error
- Target blocks probe user-agent or IP — incomplete results with partial scoring
- TLS handshake failure at target — TLS score marked as failed with error detail

## How this service works

Grade any x402 seller's payment-security posture from the outside - a read-only black-box check mapped to the 'Five Attacks on x402' failure modes. Probes the URL's 402 challenge (never pays) and scores TLS transport, gated-response cache hygiene (Attack III / cache leakage), error/info-leak hygiene, and payment-terms well-formedness, then returns a letter grade with per-check findings and an honest note on what only insider/active testing can confirm.

## Output

Returns a structured security posture report for the probed x402 endpoint, including a numeric score, TLS transport grade, cache hygiene evaluation, and per-failure-mode findings mapped to the Five Attacks on x402 taxonomy — all derived without submitting any payment.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "description": "URL of the paid resource to audit"
      },
      "method": {
       "type": "string",
       "description": "HTTP method to probe with (default GET)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "url": {
       "type": "string"
      },
      "grade": {
       "type": "string"
      },
      "score": {
       "type": "integer"
      },
      "checks": {
       "type": "array",
       "items": {
        "type": "object",
        "properties": {
         "id": {
          "type": "string"
         },
         "title": {
          "type": "string"
         },
         "attack": {
          "type": "string"
         },
         "detail": {
          "type": "string"
         },
         "status": {
          "type": "string"
         },
         "severity": {
          "type": "string"
         }
        }
       }
      },
      "status": {
       "type": "integer"
      },
      "summary": {
       "type": "string"
      },
      "reachable": {
       "type": "boolean"
      },
      "x402Version": {
       "type": "integer"
      },
      "paymentRequired": {
       "type": "boolean"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "url": "https://api.example.com/paid",
  "grade": "A",
  "score": 92,
  "checks": [
   {
    "id": "transport-tls",
    "title": "Payment challenge served over TLS",
    "attack": "credential interception",
    "detail": "https",
    "status": "pass",
    "severity": "high"
   },
   {
    "id": "cache-hygiene",
    "title": "Gated response is not shared-cacheable",
    "attack": "III - cache leakage",
    "detail": "Cache-Control: no-store, private",
    "status": "pass",
    "severity": "high"
   }
  ],
  "status": 402,
  "summary": "A (92/100) - 6 passed, 1 warning, 0 failed. Note: replay/idempotency (II) and router Sybil (IV) can't be graded from outside.",
  "reachable": true,
  "x402Version": 2,
  "paymentRequired": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-payment-security-posture-auditor-4c47a475/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent402.tools](https://www.zero.xyz/host/agent402.tools/llms.txt)