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code402 ISBN Check
x402
code402 ISBN Check is a paid API for AI agents from hcrb.in, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-11).
Validates an ISBN (International Standard Book Number) using deterministic checksum verification, returning validity, reason, and normalized form — paid per call via x402 USDC micropayment.
Price / call$0.005
Success—
StatusUnknown
How this service works
Offline deterministic checks (no ML, no scraping) for business identifiers and rental due-diligence, paid per call via x402 (gasless EIP-3009 USDC on Base). Checksum-verifiable (IBAN, LEI, VAT, ABA, ISBN, SEDOL…) vs format-only (EIN, IFSC, SWIFT/BIC…) — every response returns a scope field. Non-custodial, signed receipts. First 3 calls/day free.
Output
A JSON object with: `valid` (boolean indicating whether the ISBN passes checksum), `reason` (human-readable explanation such as 'checksum valid' or specific failure reason), `scope` (indicating whether this was a checksum-verifiable or format-only check), `normalized` (the canonical form of the ISBN), and optionally `country` and `tool` fields.
Example use cases
Catalog import ISBN gating
“Before I bulk-import this list of book ISBNs into our library system, can you validate each one to catch any typos or bad checksums? Start with 0-306-40615-2.”
E-commerce product listing check
“I'm listing books on our marketplace and want to make sure the ISBN 9780306406157 a seller submitted is actually valid — can you verify the checksum and give me the normalized form?”
Book scanning app barcode verification
“A user just scanned a barcode that read 9780140449136 — can you confirm that's a valid ISBN with a correct checksum before we look it up in our database?”
Technical details
Endpoint
POSThttps://hcrb.in/v1/tools/isbn-check/call?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a fast, offline, deterministic ISBN checksum validation without relying on external book databases or ML models. It is ideal for batch data hygiene, catalog ingestion pipelines, or any workflow where you need mathematical certainty that an ISBN is structurally correct before querying a slower or costlier lookup service. The per-call micropayment model ($0.005 USDC) and first-3-free-per-day policy make it economical for occasional or moderate-volume use. Prefer this over web-scraping-based book lookup services when you only need structural validity, not bibliographic metadata.
Side effects
- Invalid or malformed input returns valid:false with a descriptive reason
- Checksum failure returns valid:false with reason explaining the mismatch
- Payment not included or insufficient results in HTTP 402 response before processing
- Unknown or unsupported ISBN format may return format-only scope with limited validation
- Network timeout on the micropayment settlement layer
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| input | object |
Output
Schema · Response
{
"type": "json",
"schema": {
"type": "object",
"required": [
"valid",
"reason"
],
"properties": {
"tool": {
"type": "string"
},
"scope": {
"type": "string"
},
"valid": {
"type": "boolean"
},
"reason": {
"type": "string"
},
"country": {
"type": "string"
},
"normalized": {
"type": "string"
}
}
},
"example": {
"valid": true,
"reason": "checksum valid"
}
}Tags
x402
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