# Crawlspur Canonical Self-Reference Check for Pages

> Crawlspur Canonical Self-Reference Check for Pages 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 webpage (Seite) has a self-referencing canonical tag pointing to itself, as an SEO crawl audit finding.

## Facts

- Endpoint: POST https://crawlspur.halowerk.com/v1/pruef/crawlspur/canonical-selbst/seite
- 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-pages-662ba648
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_sjTs99GAk9UVF_Lw7K0YQ

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-pages-662ba648 -d '<json body>'
```

Example prompt: Check whether the page at https://example.com/blog/my-post has a self-referencing canonical tag — I need to know if its canonical link element correctly points back to itself.

## When to prefer this

Use this endpoint when you specifically need to verify the self-referencing canonical tag on a standard webpage (Seite object type). Prefer this over sitemap or robots-file canonical checks when your target is a regular HTML page. Ideal for automated SEO audits, post-migration checks, or continuous monitoring of on-page canonicalization correctness.

## Known failure modes

- URL is not publicly reachable — returns an error or empty finding
- Target page returns a non-2xx HTTP status, preventing crawl
- CSS selector matches no element, falling back to first match or failing
- Canonical tag is absent entirely, returning a negative/missing finding
- URL exceeds 2048 character limit — rejected by schema validation
- Malformed URL input causes request rejection

## How this service works

Prüft am Objekt seite den Befund selbstreferenzierende kanonische Adresse.

## Output

Returns a structured audit finding indicating whether the target page (Seite) carries a self-referencing canonical tag — i.e. whether the page's canonical link element href matches the page's own URL. Includes the detected canonical address and pass/fail status.

## 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-pages-662ba648/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)