# GSTIN Validator (code402)

> GSTIN Validator (code402) is a paid API for AI agents from hcrb.in, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-12).

Validates an Indian Goods and Services Tax Identification Number (GSTIN) using offline deterministic checksum logic, returning validity, reason, and normalized form.

## Facts

- Endpoint: POST https://hcrb.in/v1/tools/gstin-check/call?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gstin-validator-code402-5b35be35
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_3ja5XITyHWMZMlx6n5z7y

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 gstin-validator-code402-5b35be35 -d '<json body>'
```

Example prompt: Can you check whether the GSTIN '27AAPFU0939F1ZV' is valid — I need to verify this Indian supplier's tax registration before we process their invoice.

## When to prefer this

Choose this endpoint when you need fast, offline, deterministic validation of Indian GSTINs without relying on government API lookups or ML models. Ideal for invoice processing pipelines, vendor onboarding, and B2B compliance checks where you need a checksum-level verification with a signed receipt and per-call micropayment via USDC — not a live registry lookup.

## Known failure modes

- Invalid or malformed GSTIN input returns valid:false with a descriptive reason
- Missing required input field returns an error response
- Payment failure via x402 (insufficient USDC balance) blocks the call after the 3 free daily calls are exhausted
- Network timeout if the endpoint is temporarily unreachable
- Non-GSTIN identifiers passed to this endpoint return format validation errors

## How this service works

Offline deterministic checks (no ML, no scraping) for business identifiers and rental due-diligence, paid per call via x402 (gasless EIP-3009 USDC on Base). Checksum-verifiable (IBAN, LEI, VAT, ABA, ISBN, SEDOL…) vs format-only (EIN, IFSC, SWIFT/BIC…) — every response returns a scope field. Non-custodial, signed receipts. First 3 calls/day free.

## Output

Returns a JSON object with: `valid` (boolean indicating whether the GSTIN passed validation), `reason` (human-readable explanation such as 'checksum valid' or error detail), `scope` (indicating whether validation was checksum-verifiable or format-only), `normalized` (cleaned canonical form of the identifier), and `country` (always India for GSTIN). Also echoes `tool` name.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "gstin"
   ],
   "properties": {
    "gstin": {
     "type": "string",
     "description": "15-character Indian Goods and Services Tax Identification Number."
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "schema": {
  "type": "object",
  "required": [
   "valid",
   "reason"
  ],
  "properties": {
   "tool": {
    "type": "string"
   },
   "scope": {
    "type": "string"
   },
   "valid": {
    "type": "boolean"
   },
   "reason": {
    "type": "string"
   },
   "country": {
    "type": "string"
   },
   "normalized": {
    "type": "string"
   }
  }
 },
 "example": {
  "valid": true,
  "reason": "checksum valid"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gstin-validator-code402-5b35be35/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from hcrb.in](https://www.zero.xyz/host/hcrb.in/llms.txt)