# GSTIN Format Validator

> GSTIN Format Validator is a paid API for AI agents from verifyapi.hillguava.xyz, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Validates the format of a 15-character Indian GSTIN by checking state code, embedded PAN, entity type, and Luhn-mod-36 checksum

## Facts

- Endpoint: GET https://verifyapi.hillguava.xyz/verify/gstin-format/:gstin
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gstin-format-validator-70150863
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_-xCfYoVvZuxRdl-p7pjif

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-format-validator-70150863
```

Example prompt: Can you check if this GSTIN is valid: 27AAPFU0939F1ZV? I want to know if the state code, PAN, entity type, and checksum all check out before I use it on an invoice.

## When to prefer this

Use this endpoint when you need lightweight, offline-style format validation of a GSTIN before submitting it to a government API or using it on a tax invoice. It checks structural correctness (state code, PAN, entity type, checksum) without making a live lookup against the GST portal — ideal for fast pre-validation in form submissions or data pipelines.

## Known failure modes

- GSTIN not exactly 15 characters — returns format error
- invalid state code prefix — flagged in response
- malformed PAN segment in characters 3–12 — validation fails
- unrecognized entity type character at position 13 — flagged
- checksum mismatch (Luhn-mod-36 failure) — returns invalid
- payment not provided or insufficient — HTTP 402 returned

## How this service works

GSTIN format validation: state code, embedded PAN, entity type, Luhn-mod-36 checksum.

## Output

Returns a structured validation result indicating whether the 15-character GSTIN passes format checks, including whether the embedded state code is valid, the PAN segment is correctly formed, the entity type character is recognized, and the Luhn-mod-36 checksum is correct.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object",
     "required": [
      "gstin"
     ],
     "properties": {
      "gstin": {
       "type": "string",
       "description": "15-character GSTIN, e.g. 27AAPFU0939F1ZV"
      }
     }
    },
    "queryParams": {
     "type": "object",
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gstin-format-validator-70150863/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from verifyapi.hillguava.xyz](https://www.zero.xyz/host/verifyapi.hillguava.xyz/llms.txt)