Arc & Ledger Tax Reference

Screen an ITIN reason and application path

check_itin_eligibility

Read-only

Use to screen general ITIN reason categories, whether a return is commonly attached, and supporting-document requirements. Never request or process an actual ITIN, passport, or identity document.

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": {
      "has_ssn": "<has_ssn>",
      "reason": "<reason>"
    },
    "name": "check_itin_eligibility"
  }
}

Input Schema

Name	Required	Description
`reason`	Yes	Why you think a US taxpayer ID may be needed. file_us_tax_return = you must file a US return; owner_of_us_llc = you own a US LLC or corporation, which does not by itself establish a personal ITIN need; claim_treaty_benefit = a treaty claim may require a TIN; spouse_or_dependent = a US return may need a spouse or dependent TIN; third_party_withholding = a payer has a reporting or withholding requirement; open_us_bank_or_other = another reason.
`has_ssn`	Yes	Whether you already have, or are eligible for, a US Social Security Number. If yes, you cannot get an ITIN.
`is_foreign_national`	No	Whether you are a non-US citizen without US immigration status that grants an SSN. Defaults to true.

Output Schema

Name	Required	Description
`relay`	Yes	Instruction to the calling assistant: relay figures and dates verbatim (identical on every response).
`next_step`	Yes	A single review link appropriate to this server surface.
`disclaimer`	Yes	General-information disclaimer (identical on every response).
`source_url`	Yes	Official IRS or FinCEN authority to review before relying on the result.
`server_version`	No	Server release that produced this response (matches GET /version).

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 28, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds valuable context: it explicitly forbids requesting or processing actual identity documents, which is a behavioral constraint beyond the annotations.

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

Conciseness5/5

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

Two sentences, each serving a distinct purpose: one states what the tool does, the other sets a critical boundary. No wasted words, front-loaded key action.

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

Completeness5/5

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

Given the simple nature of the tool and the existence of an output schema, the description sufficiently covers the screening functionality, constraints, and purpose. No gaps identified.

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?

Schema description coverage is 100%, so baseline is 3. The description adds a high-level purpose but does not enhance parameter meaning beyond what the schema already provides for each field.

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?

The description clearly states the tool screens ITIN reason categories, return attachment, and document requirements. It uses specific verbs and resource ('screen general ITIN reason categories') and distinguishes from sibling tools which focus on other tax checks.

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?

The description explicitly says 'Use to screen' and includes a strong boundary ('Never request or process an actual ITIN...'). It implies when to use this tool for ITIN eligibility screening versus other sibling tools, though it does not explicitly name alternatives.

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

All Arc & Ledger Tax Reference tools Inspect

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