CUSIP ↔ ISIN convert & validate API

Convert between a US CUSIP and ISIN (ISIN = 'US' + CUSIP + computed check digit) in either direction AND independently validate both check digits with the correct algorithms (CUSIP modulus-10 double-add-double over base-36; ISIN Luhn over digit-expanded chars). Deterministic securities-identifier math LLMs get wrong. Answers 'convert this CUSIP to ISIN', 'what is the ISIN for CUSIP 037833100', 'is this ISIN valid', 'validate this CUSIP check digit'.

Price$0.01per request

MethodPOST

Route/v1/finance/cusip-isin

StatusLive

MIME typeapplication/json

Rate limit60/minute

CacheNo cache

financecusipisinsecuritiescheck-digitvalidationidentifierluhn

API URLhttps://x402.hexl.dev/v1/finance/cusip-isin

Integration docs

Example request

{
  "value": "037833100"
}

Example response

{
  "input": "037833100",
  "detected": "cusip",
  "cusip": "037833100",
  "isin": "US0378331005",
  "cusipValid": true,
  "isinValid": true,
  "countryCode": "US"
}

Input schema

{
  "type": "object",
  "required": [
    "value"
  ],
  "properties": {
    "value": {
      "type": "string",
      "examples": [
        "037833100",
        "US0378331005"
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}