# GTIN Barcode Check Digit Validator

> GTIN Barcode 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 2026-10-29).

Validates the check digit of a UPC-A, EAN-8, EAN-13, or GTIN-14 barcode and identifies its format.

## Facts

- Endpoint: GET https://id-validators.x402tookit.com/gtin-check?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gtin-barcode-check-digit-validator-6b5ea6cb
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UVGEjoWstWmxeIz2kBYZy

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 gtin-barcode-check-digit-validator-6b5ea6cb
```

Example prompt: Can you check whether the barcode 036000291452 is a valid barcode and tell me what format it is — UPC-A, EAN-13, or something else?

## When to prefer this

Use this endpoint when you need to verify the mathematical integrity of a retail or supply chain barcode (UPC-A, EAN-8, EAN-13, GTIN-14) before storing, displaying, or processing it. Prefer it over general-purpose regex checks because it applies the correct Luhn-style check digit algorithm per format and returns a structured verdict with the identified format name. For other identifier types (CUSIP, ISIN, ISBN, VIN, ISSN), use the sibling endpoints on the same platform.

## Known failure modes

- Missing or empty 'id' query parameter returns an error
- Non-numeric or malformed input may return invalid verdict with reasons
- Barcode length not matching any known format returns null format
- Check digit mismatch returns invalid verdict with explanation
- Network timeout or service degradation sets degraded flag

## How this service works

Validate a UPC-A, EAN-8, EAN-13 or GTIN-14 barcode check digit and name its format.

## Output

Returns a verdict (valid/invalid), the detected format (UPC-A, EAN-8, EAN-13, or GTIN-14), the normalized barcode string, its length, a human-readable summary, reasons for any failure, and metadata such as source and timestamp. A 'degraded' flag indicates partial service availability.

## 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 barcode number"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "format": {
       "type": [
        "null",
        "string"
       ]
      },
      "length": {
       "type": [
        "null",
        "number"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "normalised": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gtin-barcode-check-digit-validator-6b5ea6cb/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)