# Crawlspur Canonical Self-Reference Check for URL Rules

> Crawlspur Canonical Self-Reference Check for URL Rules is a paid API for AI agents from crawlspur.halowerk.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Checks whether a URL rule object has a self-referencing canonical address (canonical tag pointing to itself).

## Facts

- Endpoint: POST https://crawlspur.halowerk.com/v1/pruef/crawlspur/canonical-selbst/url-regel
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/crawlspur-canonical-self-reference-check-for-url-rules-efa7a60b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_BhoX9-6VE6DcG7_OmzBnI

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 crawlspur-canonical-self-reference-check-for-url-rules-efa7a60b -d '<json body>'
```

Example prompt: Check whether the page at https://example.com/blog/post-123 has a self-referencing canonical tag — I want to confirm the canonical link element points back to itself.

## When to prefer this

Use this endpoint when you specifically need to verify that a URL rule page has a self-referencing canonical tag as part of a technical SEO audit. It is purpose-built for checking the canonical self-reference finding on URL-rule objects, distinct from checking other objects like sitemaps, images, pagination, or robots files — all of which have sibling endpoints on the same service.

## Known failure modes

- URL is not publicly accessible (returns 4xx or 5xx HTTP status)
- No canonical tag found on the target URL
- URL exceeds 2048 character limit
- CSS selector matches no element or multiple elements unexpectedly
- Target server blocks crawl requests or returns timeout
- Invalid URL format provided

## How this service works

Prüft am Objekt url-regel den Befund selbstreferenzierende kanonische Adresse.

## Output

Returns a finding (Befund) indicating whether the URL rule object has a self-referencing canonical address — i.e. whether the canonical link element on the page points to the page's own URL. Typically includes pass/fail status and the detected canonical URL value.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "ziel": {
   "oneOf": [
    {
     "type": "string",
     "maxLength": 2048,
     "minLength": 1,
     "description": "Öffentliche HTTP(S)-Adresse; bei DNS-Befunden Domain oder öffentliche IP."
    },
    {
     "type": "object",
     "required": [
      "adresse"
     ],
     "properties": {
      "adresse": {
       "type": "string",
       "maxLength": 2048,
       "minLength": 1
      },
      "selektor": {
       "type": "string",
       "maxLength": 240,
       "minLength": 1,
       "description": "CSS-Selektor: genau ein Objekt, sonst erster Treffer des Objektfilters."
      },
      "vergleich": {
       "type": "string",
       "maxLength": 2048,
       "description": "Öffentliche Vergleichsadresse für Link-, Sitemap- oder Sprachbefunde."
      },
      "user_agent": {
       "type": "string",
       "pattern": "^[A-Za-z0-9_-]{1,80}$"
      },
      "dkim_selektor": {
       "type": "string",
       "pattern": "^[A-Za-z0-9_-]{1,63}$"
      }
     },
     "additionalProperties": false
    }
   ]
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/crawlspur-canonical-self-reference-check-for-url-rules-efa7a60b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from crawlspur.halowerk.com](https://www.zero.xyz/host/crawlspur.halowerk.com/llms.txt)