Arc & Ledger Tax Tools

Screen the 14-day home-rental rule

estimate_augusta_rule

Read-only

Use this when a business owner asks about the "Augusta rule," renting a home to a related business, or the fewer-than-15-day rental-income exclusion in IRC 280A(g). Screens the total rental-day limit and calculates conditional amounts while keeping the owner-side exclusion separate from the business-side deduction requirements.

Input Schema

TableJSON Schema

Name	Required	Description
`days_rented`	Yes	Total number of days during the year the dwelling is rented to anyone at a fair rental price, including days rented to your business. The IRC 280A(g) income exclusion requires fewer than 15 total rental days and that the dwelling is used as a home.
`marginal_tax_rate_pct`	No	Your combined marginal tax rate as a percent (e.g. 24 for 24%, or 33 to include state). Used to translate the deduction into a tax saving. Defaults to 22.
`fair_daily_rental_rate_usd`	Yes	The FAIR-MARKET daily rate to rent your home for a comparable business event (e.g. what a hotel meeting room or event space of similar size would charge). Must be supportable with a written quote or comparable.

Output Schema

TableJSON 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	The arcandledger.com page that backs this answer.
`server_version`	No	Server release that produced this response (matches GET /version).

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedJul 26, 2026

changedInput schema / properties / days_rented / description

Previous value: -"Number of days per year you rent your home to your business. The tax-free treatment ONLY applies at 14 days or fewer."New value: +"Total number of days during the year the dwelling is rented to anyone at a fair rental price, including days rented to your business. The IRC 280A(g) income exclusion requires fewer than 15 total rental days and that the dwelling is used as a home."

changedOutput schema / properties / next_step / description

Previous value: -"A single human handoff to the firm."New value: +"A single review link appropriate to this server surface."

Changed2 schema fields changedJul 13, 2026

addedOutput schema / properties / relay

Added value: +{
+  "description": "Instruction to the calling assistant: relay figures and dates verbatim (identical on every response).",
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "disclaimer",
-  "source_url",
-  "next_step"
-]New value: +[
+  "disclaimer",
+  "relay",
+  "source_url",
+  "next_step"
+]

Changed1 schema field changedJul 12, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "disclaimer": {
+      "description": "General-information disclaimer (identical on every response).",
+      "type": "string"
+    },
+    "next_step": {
+      "description": "A single human handoff to the firm.",
+      "properties": {
+        "label": {
+          "type": "string"
+        },
+        "url": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "label",
+        "url"
+      ],
+      "type": "object"
+    },
+    "server_version": {
+      "description": "Server release that produced this response (matches GET /version).",
+      "type": "string"
+    },
+    "source_url": {
+      "description": "The arcandledger.com page that backs this answer.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "disclaimer",
+    "source_url",
+    "next_step"
+  ],
+  "type": "object"
+}

First observedJul 8, 2026

TDQS

A4.4/5.0

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 context that the tool 'screens' limits and 'calculates conditional amounts,' which aligns with read-only behavior. It does not contradict annotations and adds useful behavioral context beyond what annotations provide.

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?

The description is three sentences, front-loads the usage scenario, and is free of filler. Every sentence contributes value: when to use, what it does, and how it handles the logic.

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?

Given the tool's complexity (tax rule screening with 3 parameters and an output schema), the description covers the core behavior and use case. It mentions calculating conditional amounts and separating owner/business aspects. The output schema fills gaps on return values, so completeness is good.

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 does not add significant meaning beyond the schema; it mentions screening day limits but does not elaborate on parameter details. The schema descriptions are already comprehensive.

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 explicitly states the tool screens the 14-day home-rental rule (IRC 280A(g)), calculates conditional amounts, and separates owner exclusion from business deduction. It clearly distinguishes this from sibling tools like estimate_rental_income by naming the specific tax rule and context.

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

Usage Guidelines5/5

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

The description begins with 'Use this when a business owner asks about...' and lists specific scenarios (Augusta rule, renting to a related business, fewer-than-15-day exclusion). It also notes the separation of owner and business sides, providing clear context for when to use this tool.

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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