# CrawlSpur Robots.txt Self-Referencing Canonical Check

> CrawlSpur Robots.txt Self-Referencing Canonical Check 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 robots.txt file contains a self-referencing canonical URL declaration, returning an SEO audit finding for the target URL.

## Facts

- Endpoint: POST https://crawlspur.halowerk.com/v1/pruef/crawlspur/canonical-selbst/robots-datei
- 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-robots-txt-self-referencing-canonical-check-750e4426
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6B3goftkM8LufLYPbqI7d

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-robots-txt-self-referencing-canonical-check-750e4426 -d '<json body>'
```

Example prompt: Check my robots.txt at https://example.com/robots.txt and tell me whether it contains a correct self-referencing canonical URL declaration.

## When to prefer this

Use this endpoint when you specifically need to audit a robots.txt file for self-referencing canonical URL declarations as part of a technical SEO workflow. It is purpose-built for this single SEO check, making it more precise than a generic crawler or full-site SEO audit tool. Prefer it for automated, per-URL SEO monitoring pipelines or pre-launch technical SEO checklists where canonical correctness in robots.txt is a required signal.

## Known failure modes

- Target URL is unreachable or returns non-200 HTTP status — check returns an error finding
- robots.txt file does not exist at the target domain — endpoint may return a not-found finding
- Malformed or non-public URL provided — input validation error
- Target URL exceeds maximum length of 2048 characters — rejected with schema validation error
- CSS selector matches zero elements — first matching element used or error returned

## How this service works

Prüft am Objekt robots-datei den Befund selbstreferenzierende kanonische Adresse.

## Output

Returns an SEO audit finding indicating whether the robots.txt file at the target URL contains a self-referencing canonical URL, including the detected value or absence of such a declaration, and any relevant diagnostic details.

## 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-robots-txt-self-referencing-canonical-check-750e4426/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)