Check a GSTIN from Claude: setting up the gstinapi MCP server

The seven tools the server exposes, the config that installs it, and what it does and does not cover.

By gstinapi.in team · Published 4 October 2026 · Last reviewed 4 October 2026

What the server is

The Model Context Protocol (MCP) is a standard way for an AI assistant to call tools. gstinapi-mcp is a small MCP server, published on npm, that exposes the gstinapi.in REST API as tools Claude can call during a conversation. Instead of copying a GSTIN into a website and pasting the result back, you ask a question and the assistant makes the call.

It runs on your machine over standard input and output (the stdio transport), and holds no logic of its own. Every tool is one pass-through GET to the REST API using your key, so what it returns is exactly what the API returns, including the same live data and the same billing. Errors come back as the API's own error text. We checked the published package, version 1.0.2, against the source on 4 October 2026 and they match.

The seven tools

ToolWhat it doesInputs
verify_gstinLive registration lookup: legal and trade name, status, taxpayer type, constitution, registration date, address. Optional profile adds jurisdiction, e-invoicing status, nature of business and additional places of business at no extra cost.gstin; optional include_profile
get_gstin_returnsReturns filed in a financial year, with period, filing date, status and ARNgstin, financial_year such as 2025-26
get_gstin_complianceThe same history summarised per return type: count, last period, months since, average filing lag. Facts only, no defaulter flaggstin, financial_year
get_gstin_filing_preferenceMonthly or quarterly filing for each quartergstin, financial_year
lookup_hsn_codeOfficial description of a 2 to 8 digit HSN or SAC code with its chapter and heading. No GST rate is returnedcode
search_hsn_codesFree-text search across HSN and SAC codesquery; optional kind and limit
get_usage_statsToday's call count for your key. Freenone

Lookups, returns, compliance and filing preference are billed at the same per-call credit price as the REST API. The complete-profile endpoint, which bundles three of these in one call, is a REST endpoint and not an MCP tool in this version. Claude can still reach the same facts by calling verify_gstin, get_gstin_returns and get_gstin_filing_preference in turn.

Installing it

  1. Create an account and copy your API key. Up to 100 lookups are free: 25 on signup and 25 for each of three setup steps, with no card needed.
  2. Add the server to your client's MCP config. The README gives this snippet for Claude Desktop (claude_desktop_config.json) and Claude Code (.mcp.json).
  3. Restart the client. There is no install step: npx downloads the package the first time it runs. It needs Node 18 or later.
  4. Ask a question that names a GSTIN, such as whether it is active, and approve the tool call when the client asks.
{
  "mcpServers": {
    "gstinapi": {
      "command": "npx",
      "args": ["-y", "gstinapi-mcp"],
      "env": { "GSTINAPI_API_KEY": "your-api-key-here" }
    }
  }
}

The key is sent as the x-api-key header. With no key set, every tool returns an error telling you to register.

What to ask

The tools map onto plain questions. "Is 33AAACC1206D1ZN active, and what is its legal name?" calls verify_gstin. "Has this vendor filed GSTR-3B for 2025-26?" calls get_gstin_returns. "Does this vendor file monthly or quarterly?" calls get_gstin_filing_preference. "What is the official description of HSN 8471?" calls lookup_hsn_code. These pairings come from the tools' own descriptions; how an assistant chooses between them in a given conversation is up to the assistant.

Two practical points. Each call is a live lookup and is billed, so an assistant asked to check a list of fifty suppliers will make fifty or more calls: for lists, the bulk upload is the cheaper and quicker route. And the results are only as reliable as the question: the server returns registration facts, not advice on what to do about them.

Which clients it is documented for

The README documents Claude Desktop and Claude Code and mentions other MCP clients only generically. We have not tested or documented it for other assistants. The server is also listed in the official MCP registry under io.github.CsoftTarun/gstinapi-mcp, where the current entry is version 1.0.2.

Frequently asked questions

What is the gstinapi MCP server?

An npm package, gstinapi-mcp, that lets an MCP-capable assistant call the gstinapi.in API as tools: verify a GSTIN, read its return history and filing preference, and look up HSN and SAC codes.

Does it work with ChatGPT?

We document it for Claude Desktop and Claude Code. Other clients that support MCP servers over stdio may be able to run it with the same config, but we have not tested or documented them, and ChatGPT is not one we document.

How much does the MCP server cost?

There is no separate charge. Tool calls use the same credits as the REST API, and every account starts with up to 100 free lookups.

Can Claude verify a GSTIN for me?

Yes, with the server installed and an API key configured, Claude can call verify_gstin on a GSTIN and report the registration status, names, taxpayer type and address returned by the live lookup.

Try it on a real GSTIN

Up to 100 free lookups: 25 on signup and 25 for each of three setup steps. No card, and they never expire.

Create a free account