# Strale ISBN Validator

> Strale ISBN Validator is a paid API for AI agents from api.strale.io, paid per call via x402, $0.0216/call, status unknown (last checked 2026-09-15).

Validates ISBN-10 or ISBN-13 numbers, checking format correctness and checksum integrity with a cryptographic audit record.

## Facts

- Endpoint: GET https://api.strale.io/x402/v2/isbn-validate
- Price: $0.0216/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/strale-isbn-validator-5892e8d5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_96rDo-eOZkSkE4Gkrraw2

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 strale-isbn-validator-5892e8d5
```

Example prompt: Can you check whether the ISBN 978-3-16-148410-0 is a valid ISBN-13?

## When to prefer this

Choose this endpoint when you need a verifiable, auditable ISBN validation with a cryptographic chain record — particularly useful in publishing pipelines, compliance workflows, or multi-agent systems where tamper-evident audit trails are required. Prefer this over simple regex checks when you need a trusted, independently-tested validation result.

## Known failure modes

- Missing 'isbn' query parameter returns a validation error
- Malformed ISBN string (wrong length, invalid characters) may return invalid result rather than an error
- Network or service downtime returns HTTP 5xx
- Invalid payment or insufficient USDC balance may block the request under x402 protocol

## How this service works

The trust layer for AI agents — 250+ independently tested data capabilities across 27 countries. Execute capabilities via REST, MCP, A2A, or x402 micropayments. Every call returns an audit record with cryptographic chain hashing.

## Output

Returns a validation result indicating whether the submitted ISBN-10 or ISBN-13 is correctly formatted and passes its checksum, along with a cryptographic audit record that chains the call for traceability.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "isbn"
     ],
     "properties": {
      "isbn": {
       "type": "string",
       "description": "ISBN-10 or ISBN-13 (e.g. 978-3-16-148410-0)"
      }
     }
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/strale-isbn-validator-5892e8d5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.strale.io](https://www.zero.xyz/host/api.strale.io/llms.txt)