# Agent402 UK Luhn Checksum Validator

> Agent402 UK Luhn Checksum Validator is a paid API for AI agents from agent402.co.uk, paid per call via x402, $0.001/call, status down (last checked 2026-09-15).

Validates a digit string using the Luhn algorithm and returns a masked version of the number in the response.

## Facts

- Endpoint: POST https://agent402.co.uk/v1/validate/luhn
- Price: $0.001/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent402-uk-luhn-checksum-validator-efe37a54
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_lqCUOiocNv2_TLgTDtrXF

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 agent402-uk-luhn-checksum-validator-efe37a54 -d '<json body>'
```

Example prompt: Can you run a Luhn checksum on the number 4532015112830366 and tell me if it's valid? Make sure the number is masked in the result.

## When to prefer this

Choose this endpoint when you need a lightweight, pay-per-call Luhn checksum validation with built-in number masking — especially useful in agent pipelines where you want to avoid logging raw card or sensitive digit strings. Prefer it over rolling your own Luhn logic when you need a reliable hosted validator with a simple POST interface and no API key setup.

## Known failure modes

- Non-digit characters in the input may cause a validation error or unexpected result
- Empty string input may return an error or false validity
- Extremely long digit strings may be rejected
- Network or payment processing errors may return a non-200 status

## How this service works

Don't burn tokens on deterministic work. Go/no-go jobs first: payout preflight, text firewall (PII/secrets), budget check — then rails, calendars, finmath. x402 USDC on Base. UK + global. agent402.co.uk — not agent402.tools. $0.001–$0.002 USDC on Base. No API keys.

## Output

Returns a boolean indicating whether the input digit string passes the Luhn checksum, along with a masked version of the number (e.g., with middle digits obscured) to avoid exposing sensitive data in logs or responses.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "number": {
   "type": "string",
   "description": "Digits to check"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "valid": true,
  "digits": 16,
  "masked": "4111********1111"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent402-uk-luhn-checksum-validator-efe37a54/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent402.co.uk](https://www.zero.xyz/host/agent402.co.uk/llms.txt)