AgentStall: Africa and global data for agents

India GSTIN validator: check a GST number and decode state and PAN

india_gstin_validate

Read-onlyIdempotent

GSTIN (India GST number) validation: checks the 15-character format and the check character, and decodes the state, the embedded PAN and the type of PAN holder (company, individual, firm, trust and others). Format check only, not a GST portal registration lookup; the number is not stored. Useful for invoices, vendor onboarding and KYB forms for Indian businesses, and for catching typos. Price: $0.002 USDC per call (x402, Base mainnet).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "gstin": "<gstin>"
    },
    "name": "india_gstin_validate"
  }
}

Input Schema

Name	Required	Description	Default
`gstin`	Yes	15-character GSTIN, e.g. 27AAPFU0939F1ZV

Schema Changelog

Changes observed during successful MCP inspections.

AddedNov 9, 2026

TDQS

A4.1/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the annotations (readOnly, idempotent, closed-world), it discloses that this is a format check rather than a registration lookup, that the number is not stored, and that each call costs $0.002 USDC via x402 on Base mainnet. Those are the traits an agent cannot infer from structured fields. It does not say what a failed check returns, so a 5 is not warranted.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

One dense but front-loaded paragraph: what is validated, what is decoded, what is excluded, then use cases and price. Every clause earns its place, though the parenthetical '(company, individual, firm, trust and others)' is slightly heavier than needed.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description compensates by enumerating the decoded outputs (state, PAN, holder type), and it covers scope, storage, and cost. It is nearly complete for a one-parameter tool; only the shape of an invalid-result response is left unstated.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The single parameter has 100% schema description coverage, including the 15-character constraint and a worked example, so the description adds no new parameter-level detail. Baseline 3 applies because the schema already carries the semantics.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource (GSTIN validation) plus exactly what is checked (15-character format, check character) and what is decoded (state, embedded PAN, PAN holder type). This is far more than a restatement of the name and lets an agent distinguish it from rate/lookup siblings immediately.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete usage contexts (invoices, vendor onboarding, KYB forms, typo catching) and explicitly bounds scope with 'Format check only, not a GST portal registration lookup'. It does not name an alternative sibling to use when a real registry lookup is needed, which keeps it below a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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