gst-validator-mcp

MCP server that validates Indian GSTIN (Goods & Services Tax Identification Numbers) — structural checks, embedded PAN extraction, state-code lookup, and the official GSTN mod-36 check character. Pure local compute, no upstream API, microsecond latencies.

For AI agents that touch Indian invoices, vendor onboarding, KYC, B2B billing, or anything else that mentions a GSTIN.

Endpoint: https://gst-validator-mcp.prakhar-cognizance.workers.dev/mcp

Tools

Example:

curl -sS -X POST https://gst-validator-mcp.prakhar-cognizance.workers.dev/mcp \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer <your-key>" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"validate_gstin","arguments":{"gstin":"27AAPFU0939F1ZV"}}}'

Returns:

{
  "valid": true,
  "state": "Maharashtra",
  "state_code": "27",
  "pan": "AAPFU0939F",
  "entity_code": "1",
  "check_char": "V"
}

Related MCP server: KYC MCP Server

Install in Cursor / Claude Desktop / Cline

Add to your MCP config (e.g. ~/.cursor/mcp.json, claude_desktop_config.json):

{
  "mcpServers": {
    "gst-validator": {
      "url": "https://gst-validator-mcp.prakhar-cognizance.workers.dev/mcp",
      "headers": { "Authorization": "Bearer <your-key>" }
    }
  }
}

Without a key, you get the free tier (100 calls/month, 10/min) keyed off your client IP.

Pricing

Subscribe at https://gst-validator-mcp.prakhar-cognizance.workers.dev/upgrade?tier=solo. Powered by Dodo Payments as merchant of record — Dodo handles GST/VAT remittance worldwide.

GSTIN format reference

A GSTIN is 15 characters drawn from [0-9A-Z]:

The check-character algorithm is the one documented by GSTN: multiply each base-36 code-point by an alternating factor of 2,1,2,1,... walking right-to-left, fold each product as (p/36) + (p%36), sum, and the check code-point is (36 - sum%36) % 36.

Self-service

• GET /account (with Authorization: Bearer <key>) — current tier, usage, portal link.

• POST /account/rotate — revoke the current key and mint a new one on the same subscription.

• Customer portal — manage / cancel / update payment method via Dodo.

Lost your key? Email prakshatechnologies@gmail.com with your Dodo subscription ID.

License

MIT © 2026 Prakhar Gupta · prakshatechnologies@gmail.com