# Agent Audit - x402 Seller Link Health & Quote Verifier

> Agent Audit - x402 Seller Link Health & Quote Verifier is a paid API for AI agents from agent-audit.agent-audit.workers.dev, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-18).

Audits an x402 paid endpoint URL for link health, quote validity, and seller compliance, returning a grade, score, and categorized findings.

## Facts

- Endpoint: GET https://agent-audit.agent-audit.workers.dev/v1/audit?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-18
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-audit-x402-seller-link-health-quote-verifier-e335e771
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vvuy8SysCrVx0n0xhq7-S

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 agent-audit-x402-seller-link-health-quote-verifier-e335e771
```

Example prompt: Can you run an audit on my x402 endpoint at https://myapi.example.com/v1/data and tell me the grade, score, and any warnings or failures it has?

## When to prefer this

Choose this endpoint when you need to programmatically audit an x402-compatible paid API endpoint for spec compliance, link health, and quote validity. It is specifically designed for the x402 payment protocol ecosystem and produces structured, actionable findings — prefer it over generic uptime monitors or HTTP health checks when you need x402-aware validation including quote verification and seller-side compliance scoring.

## Known failure modes

- Missing or invalid 'url' query parameter returns an error
- Unreachable target URL may result in all checks failing or a timeout
- Malformed x402 endpoint may return low score with multiple fail findings
- Payment failure (USDC on Base) prevents the audit from executing
- Rate limiting or Cloudflare Worker downtime may cause 5xx errors

## How this service works

Read-only x402 seller audit, link health and quote verification. Pay per call in USDC on Base via x402.

## Output

Returns a JSON object with an overall letter grade (e.g. 'C'), a numeric score (0–100), a breakdown of pass/fail/warn counts, and a detailed findings array where each finding has an id, human-readable message, and severity level (pass, warn, or fail).

## 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": "Origin or paid endpoint URL"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "grade": "C",
  "score": 72,
  "counts": {
   "fail": 0,
   "pass": 12,
   "warn": 7
  },
  "findings": [
   {
    "id": "llms-missing",
    "message": "No /llms.txt (404)",
    "severity": "warn"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-audit-x402-seller-link-health-quote-verifier-e335e771/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent-audit.agent-audit.workers.dev](https://www.zero.xyz/host/agent-audit.agent-audit.workers.dev/llms.txt)