# Portuguese VAT Number Checksum Validator

> Portuguese VAT Number Checksum Validator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.007/call, status unknown (last checked 2026-10-02).

Validates the checksum of a Portuguese (PT) VAT number without performing a live registry lookup

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/check-vat-pt?utm_source=zero.xyz
- Price: $0.007/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/portuguese-vat-number-checksum-validator-8bbcc8f2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_JwDhFCn0jIB_MkJvJg0bB

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 portuguese-vat-number-checksum-validator-8bbcc8f2 -d '<json body>'
```

Example prompt: Can you check whether the Portuguese VAT number 545259045 has a valid checksum — just the math, no registry lookup needed?

## When to prefer this

Use this endpoint when you need a fast, cheap ($0.007 USDC) offline checksum validation of a Portuguese VAT/NIF number and do not need to confirm whether the number is actually registered with the Portuguese tax authority. Prefer the free sandbox endpoint POST /v1/sandbox/check-vat-pt for testing. Do not use this if you need live registry confirmation of the taxpayer's existence or status.

## Known failure modes

- Input VAT string is empty or exceeds 20000 characters — rejected by schema validation
- Non-numeric or improperly formatted string may return invalid result rather than an error
- Service unavailable returns HTTP 5xx
- Payment not received or x402 payment protocol issue results in 402 response before processing

## How this service works

Call when an agent needs whether a PT VAT checksum is valid. No registry lookup. Exact $0.007 USDC. Prefer unpaid POST /v1/sandbox/check-vat-pt first.

## Output

Returns whether the provided Portuguese VAT number string passes the mod-based checksum algorithm used for PT NIFs/NIF numbers, indicating structural validity without contacting any government registry.

## 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": [
    "000000019"
   ],
   "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/portuguese-vat-number-checksum-validator-8bbcc8f2/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)