# Agent Tools – Link Health Check & Security Header Audit

> Agent Tools – Link Health Check & Security Header Audit is a paid API for AI agents from agents.crowdspark.me, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-31).

Checks a public URL by following redirects hop-by-hop (up to 8), detecting loops and HTTPS downgrades, and reporting final status, content type, server info, caching, and a security-header grade (HSTS, CSP, nosniff, framing, referrer, permissions).

## Facts

- Endpoint: GET https://agents.crowdspark.me/v1/web/check?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-tools-link-health-check-security-header-audit-64b7ee21
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_O54YKGnwZF3DUoXOaTsdG

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-tools-link-health-check-security-header-audit-64b7ee21
```

Example prompt: Can you check the link https://example.com/ — follow all its redirects, tell me where it ends up and whether it's safe, and give me a security header grade for the final destination?

## When to prefer this

Choose this endpoint when you need a detailed, hop-by-hop redirect trace combined with a security-header audit in a single call. It is ideal for pre-publication link safety checks, compliance audits of security headers, or detecting HTTPS downgrade attacks on redirects. Prefer it over a simple HTTP HEAD check when you need the full redirect chain, timing data per hop, and a graded security-header report. It complements a page-content reader (which fetches body content) but is focused purely on transport-layer and header-level health.

## Known failure modes

- Private or non-public IP/host rejected — only public hosts are supported
- More than 8 redirects causes the chain to be truncated or flagged as a loop
- Redirect loop detected and flagged in verdict field
- Target host is unreachable or DNS fails — returns an error verdict
- Very slow targets may time out before all hops complete
- Non-HTTP/HTTPS schemes are not supported

## How this service works

Pay-per-call utilities for AI agents over x402, USDC on Base.

## Output

Returns a JSON object with the full redirect chain (each hop's URL, HTTP status, location header, and timing in ms), total elapsed time, final URL and status, content type, HTTPS flag, HTTPS-downgrade flag, redirect count, server header, and a security-header assessment including a letter grade (A/B/C/F), numeric score, list of present headers (e.g. strict-transport-security, content-security-policy), and list of missing headers (e.g. permissions-policy).

## 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": "Public http(s) URL to check"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "url": "http://github.com/",
  "hops": [
   {
    "ms": 40,
    "url": "http://github.com/",
    "status": 301,
    "location": "https://github.com/"
   },
   {
    "ms": 120,
    "url": "https://github.com/",
    "status": 200,
    "location": null
   }
  ],
  "https": true,
  "server": "github.com",
  "verdict": "ok_after_redirect",
  "total_ms": 160,
  "final_url": "https://github.com/",
  "redirects": 1,
  "content_type": "text/html; charset=utf-8",
  "final_status": 200,
  "security_headers": {
   "grade": "A",
   "score": 90,
   "missing": [
    "permissions-policy"
   ],
   "present": [
    "strict-transport-security",
    "content-security-policy"
   ]
  },
  "downgraded_to_http": false
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-tools-link-health-check-security-header-audit-64b7ee21/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agents.crowdspark.me](https://www.zero.xyz/host/agents.crowdspark.me/llms.txt)