# ISIN Check Digit Validator

> ISIN Check Digit Validator is a paid API for AI agents from id-validators.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Validates the check digit of a securities ISIN and splits it into its country code and national security identifier number (NSIN).

## Facts

- Endpoint: GET https://id-validators.x402tookit.com/isin-check?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/isin-check-digit-validator-b8c69190
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_04XPyiAlVzBUsge2OpqWu

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 isin-check-digit-validator-b8c69190
```

Example prompt: Can you validate the ISIN US0378331005 — check its check digit, tell me if it's valid, and split out the country code and national security number?

## When to prefer this

Use this endpoint when you need to validate a specific ISIN's check digit and decompose it into its constituent parts (country code, NSIN, CUSIP for US securities). Prefer this over a generic format regex check when you need authoritative check-digit validation per the ISO 6166 algorithm.

## Known failure modes

- Missing or empty 'id' query parameter returns an error
- Malformed ISIN (wrong length or non-alphanumeric characters) returns invalid verdict with reasons
- Network timeout or upstream service unavailability
- Payment failure via x402 protocol results in 402 response before processing

## How this service works

Validate a securities ISIN check digit and split it into country code and national security number.

## Output

Returns a verdict (valid/invalid), normalised ISIN string, country code, NSIN, CUSIP if the issuer is US-based, a summary of the validation outcome, an array of reasons if invalid, an asOf timestamp, and a disclaimer. The 'degraded' flag indicates if the check ran with reduced confidence.

## 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"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "id"
     ],
     "properties": {
      "id": {
       "type": "string",
       "description": "The ISIN"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "nsin": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "cusipIfUS": {
       "type": [
        "null",
        "string"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "normalised": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "countryCode": {
       "type": [
        "null",
        "string"
       ]
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/isin-check-digit-validator-b8c69190/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from id-validators.x402tookit.com](https://www.zero.xyz/host/id-validators.x402tookit.com/llms.txt)