# Canonical URL Declarations — Empty Value Report

> Canonical URL Declarations — Empty Value Report is a paid API for AI agents from market.datapackvibe.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-21).

Parses a webpage or HTML snippet to identify canonical URL link elements that have empty or missing href values

## Facts

- Endpoint: POST https://market.datapackvibe.com/x402/assistant-bx-web-canonical-empty?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/canonical-url-declarations-empty-value-report-2d444210
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_tLUlRY3GErt_i46PwIWQe

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 canonical-url-declarations-empty-value-report-2d444210 -d '<json body>'
```

Example prompt: Check this page for any canonical link elements that have empty or missing href values — use the URL https://example.com/product-page and look for elements with the attribute id set to 'main-canonical'.

## When to prefer this

Use this endpoint when you need lightweight, static HTML parsing to detect empty or missing canonical URL declarations on a single page — ideal for SEO audits, pre-publish QA checks, or CMS template validation where JavaScript rendering is not required and cost efficiency matters.

## Known failure modes

- URL is inaccessible, behind a login, or returns a non-200 response
- HTML exceeds 100,000 character limit
- JavaScript-rendered canonical tags not captured (static parsing only)
- Malformed HTML may cause incomplete parsing
- Invalid attribute pattern (must start with a letter, alphanumeric/colon/underscore/hyphen only)
- No canonical elements found returns an empty result set

## How this service works

Canonical URL declarations — Empty value report: Empty value report for Canonical URL declarations. One public HTTPS page or supplied HTML; static parsing, no JavaScript rendering, login or access bypass. Specialised preset in a shared 50-profile, 20-operation engine. 0.01 USDC includes one bounded empty value report result.

## Output

Returns an empty value report identifying any canonical link elements in the provided URL or HTML where the href attribute is blank or absent, including element identifiers and relevant attribute details to help diagnose SEO or markup issues.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "default": "",
   "maxLength": 2048
  },
  "html": {
   "type": "string",
   "default": "<!doctype html><html><head></head><body><link rel=\"canonical\" href=\"https://www.iana.org/help/example-domains\" id=\"sample\"></body></html>",
   "maxLength": 100000
  },
  "term": {
   "type": "string",
   "default": "product",
   "maxLength": 100,
   "minLength": 1
  },
  "attribute": {
   "type": "string",
   "default": "id",
   "pattern": "^[a-zA-Z][a-zA-Z0-9:_-]{0,49}$",
   "maxLength": 50
  },
  "previous_texts": {
   "type": "array",
   "items": {
    "type": "string",
    "default": "",
    "maxLength": 1000
   },
   "default": [
    "Older example"
   ],
   "maxItems": 200,
   "minItems": 0
  },
  "attribute_value": {
   "type": "string",
   "default": "sample",
   "maxLength": 200
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/canonical-url-declarations-empty-value-report-2d444210/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from market.datapackvibe.com](https://www.zero.xyz/host/market.datapackvibe.com/llms.txt)