# Polish NIP Format & Checksum Validator (x402)

> Polish NIP Format & Checksum Validator (x402) is a paid API for AI agents from validate.crewofthecaptain.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-12).

Validates the format and checksum of a Polish NIP (tax identification number) via a pay-per-call API using x402 micropayments.

## Facts

- Endpoint: POST https://validate.crewofthecaptain.com/api/validate/pl-nip?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/polish-nip-format-checksum-validator-x402-fbc3aa8b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_dcs17-zNmGwz2QNu682nd

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-nip-format-checksum-validator-x402-fbc3aa8b -d '<json body>'
```

Example prompt: Can you check whether this Polish NIP number is valid: 5260001483? I need to confirm it passes the checksum before I add this supplier to our system.

## When to prefer this

Choose this endpoint when you specifically need to validate Polish NIP (tax identification) numbers with checksum verification, particularly in workflows involving Polish business partners, invoicing, supplier onboarding, or CRM data cleanup. It is ideal for pay-per-call usage at $0.001/call without subscription overhead. Use sibling endpoints on the same service for IBAN, EU VAT, REGON, PESEL, or email validation.

## Known failure modes

- Invalid or malformed NIP string returns valid:false with a reason describing the format or checksum failure
- Empty or missing 'value' field may return a validation error
- Non-string or overlong input (>512 chars) rejected by schema
- Payment failure via x402 results in HTTP 402 before validation occurs
- Network timeout or service unavailability returns HTTP 5xx

## How this service works

Format and checksum validation for IBAN, EU VAT, Polish NIP/REGON/PESEL and email, pay-per-call via x402. Only $0.001 (0.1 cent) per check, paid via x402 in USDC on Base.

## Output

Returns a JSON object with: 'type' (pl-nip), 'valid' (boolean indicating whether the NIP passes format and checksum rules), 'reason' (a string explaining the result or error, e.g. 'ok' or a specific failure reason), and 'normalized' (the canonical normalized form of the NIP number).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "value": {
   "type": "string",
   "maxLength": 512
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "type": "pl-nip",
  "valid": true,
  "reason": "ok",
  "normalized": "…"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/polish-nip-format-checksum-validator-x402-fbc3aa8b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from validate.crewofthecaptain.com](https://www.zero.xyz/host/validate.crewofthecaptain.com/llms.txt)