# ISSN Regex Extractor

> ISSN Regex Extractor is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-02).

Extracts up to 20 ISSN tokens from a given text string using regex matching, returning all found identifiers.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/regex-issn?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/issn-regex-extractor-49f3d4aa
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_4CKsuXE7UgDtRsj0Kw_Eu

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 issn-regex-extractor-49f3d4aa -d '<json body>'
```

Example prompt: Can you pull out all the ISSN numbers from this text? Here it is: 'The journal (ISSN 1234-5678) and its digital edition (ISSN 8765-4321) are both indexed in the database.'

## When to prefer this

Choose this endpoint when you need to extract ISSN identifiers from text without any network dependency — it runs a pure regex match server-side, making it fast and deterministic. Prefer the free sandbox endpoint POST /v1/sandbox/regex-issn for testing before committing to paid calls. Use this over general-purpose NLP or entity extraction services when you specifically need ISSN serial identifiers with a strict cap of 20 results and predictable $0.01 USDC pricing per call.

## Known failure modes

- Empty match list returned (but still billed $0.01 USDC) when no ISSN patterns are found in the text
- Input text exceeds 100,000 character limit, causing a validation error
- Malformed or non-standard ISSN-like strings may not be captured if they deviate from the expected regex pattern
- Payment failure if the agent's USDC balance is insufficient
- Only the first 20 matches are returned even if more ISSNs exist in the text

## How this service works

Call when an agent needs ISSN tokens extracted from text, capped at 20 matches. An empty match list is billed. No network. Exact $0.01 USDC. Prefer unpaid POST /v1/sandbox/regex-issn first.

## Output

Returns a JSON list of up to 20 ISSN token strings found in the input text. If no ISSNs are present, an empty list is returned — note that an empty result is still billed. Matching is done via regex with no network calls.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "text": {
   "type": "string",
   "examples": [
    "1234-5678"
   ],
   "maxLength": 100000,
   "minLength": 1,
   "description": "Input for this SKU. The route description says whether it is plain text, a URL, base64 bytes, or an already-encoded token."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/issn-regex-extractor-49f3d4aa/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)