# GS1 Check Digit Calculator

> GS1 Check Digit Calculator is a paid API for AI agents from trade.chainverdict.xyz, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-15).

Computes the GS1 check digit for a code body (GTIN, SSCC, etc.) that is missing its final check digit.

## Facts

- Endpoint: GET https://trade.chainverdict.xyz/v1/gtin/checkdigit
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gs1-check-digit-calculator-ca03b791
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_wxEnmKQlDYte_fQWYPJYc

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 gs1-check-digit-calculator-ca03b791
```

Example prompt: I have a GTIN body '07612345678' that's missing its GS1 check digit — can you compute what the last digit should be?

## When to prefer this

Use this endpoint when you have a GS1 code body (GTIN-8/12/13/14, SSCC, etc.) that is missing only its terminal check digit and you need to compute it programmatically. Prefer this over a full GTIN validation endpoint when you don't yet have the check digit and need to generate rather than verify it.

## Known failure modes

- Invalid or non-numeric code body returns an error
- Code body of incorrect length for the GS1 key type may produce unexpected results
- Missing required 'body' query parameter results in a validation error
- Malformed request returns HTTP 400

## How this service works

Compute the GS1 check digit for a code body missing it.

## Output

Returns the computed GS1 check digit (a single numeric digit, 0–9) for the supplied code body, allowing the caller to reconstruct the complete, valid GS1 identifier.

## 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": [
      "body"
     ],
     "properties": {
      "body": {
       "type": "string",
       "description": "GS1 key body without its check digit"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "additionalProperties": true
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gs1-check-digit-calculator-ca03b791/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from trade.chainverdict.xyz](https://www.zero.xyz/host/trade.chainverdict.xyz/llms.txt)