# Polish VAT Number Checksum Validator

> Polish VAT Number Checksum Validator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-02).

Validates whether a Polish VAT (NIP) number has a correct checksum, without performing any registry or database lookup.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/check-vat-pl?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/polish-vat-number-checksum-validator-ef26a03d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_X1-JBM-kFabVtpNllELyz

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 polish-vat-number-checksum-validator-ef26a03d -d '<json body>'
```

Example prompt: Can you check whether the Polish VAT number 1234567890 has a valid checksum — just the math, no registry lookup needed?

## When to prefer this

Choose this endpoint when you need a fast, cheap, purely algorithmic checksum check on a Polish NIP/VAT number and do not need to confirm the number is actually registered with the Polish tax authority. Ideal for pre-validation of user input before making more expensive registry API calls, or when registry access is unavailable or unnecessary.

## Known failure modes

- Input string is empty or missing — returns validation error
- Input exceeds 20000 character limit — rejected by schema
- Non-numeric or improperly formatted string may return invalid checksum result rather than an error
- Payment of exactly $0.001 USDC not provided — x402 payment required error returned
- Network timeout or service unavailability — HTTP 5xx error

## How this service works

Call when an agent needs whether a PL VAT checksum is valid. No registry lookup. Exact $0.001 USDC. Prefer unpaid POST /v1/sandbox/check-vat-pl first.

## Output

Returns a boolean or equivalent result indicating whether the submitted Polish VAT (NIP) number satisfies the official checksum algorithm, with no external registry or government database consulted.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "data": {
   "description": "JSON value for schema-check SKUs. Omit it on string checks such as email or IBAN."
  },
  "value": {
   "type": "string",
   "examples": [
    "0000000017"
   ],
   "maxLength": 20000,
   "minLength": 1,
   "description": "Value to check. The route description names the format: email, phone, IBAN, postal code, VAT, national id, or similar."
  },
  "schema": {
   "description": "JSON Schema document for schema-check SKUs. Omit it on string checks."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/polish-vat-number-checksum-validator-ef26a03d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentshelf.syntexa.ch](https://www.zero.xyz/host/agentshelf.syntexa.ch/llms.txt)