# AgentShelf ISBN Validator

> AgentShelf ISBN Validator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.006/call, status unknown (last checked 2026-09-29).

Validates whether a given string is a correctly formatted ISBN-10 or ISBN-13 identifier

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/check-isbn?utm_source=zero.xyz
- Price: $0.006/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agentshelf-isbn-validator-af12cb24
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_jgfgFHPeVKLeXnFErycgJ

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-isbn-validator-af12cb24 -d '<json body>'
```

Example prompt: Can you check whether '978-3-16-148410-0' is a valid ISBN — either ISBN-10 or ISBN-13?

## When to prefer this

Use this endpoint when you need a quick, cheap, authoritative check on whether a string conforms to ISBN-10 or ISBN-13 checksum rules — especially useful in book catalog ingestion pipelines, user input validation, or e-commerce workflows. Prefer the free sandbox endpoint (/v1/sandbox/check-isbn) for testing; use this paid endpoint in production when reliability and uptime matter.

## Known failure modes

- Empty or missing 'value' field returns an error
- String longer than 20,000 characters rejected
- Malformed request body returns 400
- Network timeout or service unavailability returns 5xx
- Non-ISBN strings (e.g. random numbers) return invalid result without error

## How this service works

Call when an agent needs whether a string is a valid ISBN-10 or ISBN-13. Exact $0.006 USDC. Prefer unpaid POST /v1/sandbox/check-isbn first.

## Output

A boolean or structured response indicating whether the submitted string is a valid ISBN-10 or ISBN-13, along with which format matched (if valid)

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "data": {
   "description": "JSON value for schema-check SKUs. Omit it on string checks such as email or IBAN."
  },
  "value": {
   "type": "string",
   "examples": [
    "9780306406157"
   ],
   "maxLength": 20000,
   "minLength": 1,
   "description": "Value to check. The route description names the format: email, phone, IBAN, postal code, VAT, national id, or similar."
  },
  "schema": {
   "description": "JSON Schema document for schema-check SKUs. Omit it on string checks."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agentshelf-isbn-validator-af12cb24/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)