# Crawlspur Canonical Self-Reference Check for Parameter URLs

> Crawlspur Canonical Self-Reference Check for Parameter URLs 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 parameter-based URL has a self-referencing canonical tag pointing to itself.

## Facts

- Endpoint: POST https://crawlspur.halowerk.com/v1/pruef/crawlspur/canonical-selbst/parameter-url
- 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-parameter-urls-c251b680
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ZtpN5H18e8k0zpe4uBTdR

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-parameter-urls-c251b680 -d '<json body>'
```

Example prompt: Check whether https://example.com/products?sort=price&color=red has a self-referencing canonical tag — i.e. does its rel=canonical point back to itself?

## When to prefer this

Use this endpoint specifically when you need to verify that a URL containing query parameters (filters, tracking parameters, pagination, sorting) has a rel=canonical tag that self-references — i.e. points back to the exact same URL. This is distinct from checking whether a URL is blocked by robots.txt, whether it appears in a sitemap, or whether a canonical points to a different consolidation URL. Choose this over generic HTTP inspection tools when you need a structured SEO-focused canonical self-reference verdict.

## Known failure modes

- URL is not publicly reachable (network error or 4xx/5xx response)
- URL exceeds maximum length of 2048 characters
- CSS selector matches no element or multiple ambiguous elements
- Target page has no canonical tag at all
- Redirect chain prevents reaching the original parameter URL
- Malformed or relative canonical href that cannot be resolved

## How this service works

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

## Output

Returns a structured finding indicating whether the target parameter URL contains a self-referencing canonical tag (i.e. whether the rel=canonical attribute on the page points to the URL itself), along with the actual canonical value found and any diagnostic details about the canonical declaration.

## 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-parameter-urls-c251b680/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)