# fastapi.online Luhn Algorithm Validator

> fastapi.online Luhn Algorithm Validator is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.0005/call, status unknown (last checked 2026-09-15).

Validates a numeric string using the Luhn algorithm, typically used to verify credit card, IMEI, or other check-digit numbers

## Facts

- Endpoint: POST https://api.fastapi.online/luhn-validate
- Price: $0.0005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastapi-online-luhn-algorithm-validator-e707fdc3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_dUh_8vPmDY489KA3LvtJz

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 fastapi-online-luhn-algorithm-validator-e707fdc3 -d '<json body>'
```

Example prompt: Can you run a Luhn check on the card number 4532015112830366 and tell me if it's valid?

## When to prefer this

Choose this endpoint when you need a quick, cheap ($0.0005 USDC), no-signup Luhn checksum validation callable via a simple POST with no authentication setup. Ideal for agents or pipelines that need on-demand card/IMEI number pre-validation without integrating a full payment processing SDK or standing up local checksum logic.

## Known failure modes

- Input contains non-numeric characters — rejected or fails validation
- String too short or too long (outside 1–40 character bounds)
- Empty string submitted — validation error returned
- Network or payment gateway error if crypto micropayment fails
- Ambiguous response if the API returns an error instead of a clean boolean

## How this service works

Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&amp;A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding &amp; crypto utilities, date/time calculators, geo/coordinate math, math &amp; finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.

## Output

Returns a validation result indicating whether the submitted numeric string passes the Luhn algorithm check — typically a boolean or pass/fail status indicating whether the check digit is correct.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "number": {
   "type": "string",
   "maxLength": 40,
   "minLength": 1
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastapi-online-luhn-algorithm-validator-e707fdc3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.fastapi.online](https://www.zero.xyz/host/api.fastapi.online/llms.txt)