# H4 Invisible Character Flags Extractor

> H4 Invisible Character Flags Extractor is a paid API for AI agents from market.datapackvibe.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-13).

Parses HTML to detect and flag invisible Unicode characters within level-four heading (h4) elements, optionally filtered by a search term, attribute, or prior text context.

## Facts

- Endpoint: POST https://market.datapackvibe.com/x402/assistant-bx-web-h4-unicode?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/h4-invisible-character-flags-extractor-1254fda8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_y6-K48grgg_xN25c8kVDo

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 h4-invisible-character-flags-extractor-1254fda8 -d '<json body>'
```

Example prompt: Can you check the page at https://example.com/docs for any invisible or hidden Unicode characters inside its h4 headings — specifically ones that match the attribute id with value 'section-one' and the term 'guide'?

## When to prefer this

Choose this endpoint when you need to specifically audit level-four HTML headings for invisible Unicode characters — such as zero-width spaces, soft hyphens, or other hidden glyphs — using static HTML parsing without browser rendering. Prefer it over generic text scanners when the target is scoped to h4 elements with optional attribute or term filtering, and when you can supply a URL or raw HTML directly.

## Known failure modes

- URL is unreachable or returns non-200 status — no content to parse
- HTML exceeds 100,000 character limit — input rejected
- No h4 headings found matching the specified term or attribute — empty result
- Invalid attribute name format — rejected by pattern validation
- URL requires JavaScript rendering or login — static parser returns incomplete content
- Previous texts array exceeds 200 items — input rejected

## How this service works

Level-four headings — Invisible character flags: Invisible character flags for Level-four headings. 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 invisible character flags result.

## Output

Returns a bounded result indicating whether invisible Unicode characters were detected within matching h4 heading elements, along with flags identifying the nature and location of those characters relative to the searched term, attribute, and prior text context.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "default": "",
   "maxLength": 2048
  },
  "html": {
   "type": "string",
   "default": "<!doctype html><html><head></head><body><h4 id=\"sample\" data-kind=\"example\">Example product guide</h4></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/h4-invisible-character-flags-extractor-1254fda8/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)