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agent402.co.uk validate isbn
https://agent402.co.uk/v1/validate/isbn
answers 402
Agent402. ISBN-10 / ISBN-13 check digit (ISO 2108). Book/catalog agents — checksum only, not registry lookup. $0.001 pure leaf.
We sent a real
POST request to this endpoint and it
answered 402 with payment requirements we could parse.
- Price
- $0.001
- Network
- base
- Pay to
- 0x9EF92b278a3867C429751390EC427736eB4BABB2
- Spec dialect
- v2 (declares x402Version 2)
- Transport
- PAYMENT-REQUIRED header
- HTTP method
- POST
- Response latency
- 131 ms
- Payment options
- 1 usable of 1
- Last checked
- 2026-08-15T14:27:00.654Z (1h ago)
- Category
- search
Re-check it yourself:
curl "https://api.the402.dev/validate?url=https%3A%2F%2Fagent402.co.uk%2Fv1%2Fvalidate%2Fisbn"