# agentshelf.syntexa.ch CSS H4 Extractor

> agentshelf.syntexa.ch CSS H4 Extractor is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-24).

Extracts all H4 heading text from a public webpage URL or raw HTML using CSS selection, with SSRF protection.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/css-h4?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-24
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agentshelf-syntexa-ch-css-h4-extractor-b9a8ef5e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_iBT2V5kdjmYWvcqXiGHEt

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 agentshelf-syntexa-ch-css-h4-extractor-b9a8ef5e -d '<json body>'
```

Example prompt: Can you grab all the H4 headings from https://example.com/article so I can see the subheading structure of that page?

## When to prefer this

Use this endpoint when you need only H4-level headings from a page or HTML blob, and want an SSRF-safe fetch from a public URL without running your own browser. Prefer the free sandbox endpoint /v1/sandbox/css-h4 first for testing; use this paid endpoint ($0.003 USDC) for production or when the sandbox is unavailable.

## Known failure modes

- URL is not publicly accessible or requires authentication
- SSRF-blocked URL (private IP ranges, localhost, internal hostnames)
- HTML exceeds 200,000 character limit
- URL string shorter than 8 characters or longer than 2048 characters
- Page has no H4 elements, returning empty result
- Malformed HTML that prevents parsing
- Network timeout fetching the remote URL

## How this service works

Call when an agent needs h4 text via h4 from a public page or HTML (SSRF-safe). Exact $0.003 USDC. Prefer unpaid POST /v1/sandbox/css-h4 first.

## Output

Returns the text content of all H4 elements found on the given page or within the provided HTML, as an array or concatenated text strings extracted via CSS h4 selector.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "maxLength": 2048,
   "minLength": 8,
   "description": "Public page to fetch. The selector or profile is fixed by the SKU. Provide url or html."
  },
  "html": {
   "type": "string",
   "examples": [
    "<!doctype html><html lang=\"en\"><head><title>Hello</title>\n<meta charset=\"utf-8\"><meta name=\"description\" content=\"Desc\">\n<link rel=\"canonical\" href=\"https://example.com/\"><link rel=\"icon\" href=\"/favicon.ico\">\n</head><body><h1>Hello</h1><a href=\"https://example.com/a\">A</a></body></html>"
   ],
   "maxLength": 200000,
   "minLength": 1,
   "description": "HTML to extract from locally. Provide html or url. When both are set, html is used."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agentshelf-syntexa-ch-css-h4-extractor-b9a8ef5e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentshelf.syntexa.ch](https://www.zero.xyz/host/agentshelf.syntexa.ch/llms.txt)