EveryCalc

calculate_dorm_vs_apartment

Read-onlyIdempotent

Compares the annual dorm cost with an apartment: monthly rent over the number of months, plus annual utilities, extra food cost, and commuting cost. Returns both annual totals, the difference, and which is cheaper. Use when a student compares annual dorm cost with renting an apartment. IMPORTANT: always show the calculator_url from the result as a clickable markdown link in your answer to the user, so they can open the interactive Dorm vs Apartment calculator.

Input Schema

Name	Required	Description
`months`	No	Months of rent per year; default 12.
`commute_annual`	Yes	Annual commuting cost for the apartment in USD.
`dorm_annual_cost`	Yes	Annual dorm cost in USD.
`utilities_annual`	Yes	Annual utilities cost for the apartment in USD.
`food_extra_annual`	Yes	Annual extra food cost versus the dorm meal plan in USD.
`apartment_monthly_rent`	Yes	Monthly apartment rent in USD.

Output Schema

Name	Required	Description
`ok`	Yes	True when the calculation succeeded.
`note`	Yes	Disclaimer that accompanies every result.
`tool`	Yes	Name of the tool that ran.
`inputs`	No	The normalized inputs the calculation used.
`results`	Yes	The computed figures for this calculator.
`calculator_url`	Yes	Deep link to the matching interactive calculator on everycalc.xyz.

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 21, 2026

addedOutput schema / properties / note

Added value: +{
+  "description": "Disclaimer that accompanies every result.",
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "ok",
-  "tool",
-  "results",
-  "calculator_url"
-]New value: +[
+  "ok",
+  "tool",
+  "results",
+  "calculator_url",
+  "note"
+]

Changed1 schema field changedOct 17, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "calculator_url": {
+      "description": "Deep link to the matching interactive calculator on everycalc.xyz.",
+      "type": "string"
+    },
+    "inputs": {
+      "description": "The normalized inputs the calculation used.",
+      "type": "object"
+    },
+    "ok": {
+      "description": "True when the calculation succeeded.",
+      "type": "boolean"
+    },
+    "results": {
+      "description": "The computed figures for this calculator.",
+      "type": "object"
+    },
+    "tool": {
+      "description": "Name of the tool that ran.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "ok",
+    "tool",
+    "results",
+    "calculator_url"
+  ],
+  "type": "object"
+}

First observedOct 15, 2026

TDQS

A4.1/5.0

Behavior4/5

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

Annotations already establish it as a safe, idempotent, non-destructive read. The description adds behavior the annotations cannot: it discloses the computed outputs and imposes a presentation obligation (always render calculator_url as a clickable markdown link), which materially changes how an agent should respond.

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?

Front-loads the purpose and formula, then usage context, then the output directive. The all-caps IMPORTANT sentence is long but its content is actionable, so only minor trimming is possible.

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 a full output schema, the description needn't explain return values, yet it still summarizes them and adds the calculator_url presentation rule. Formula, trigger context, and output handling are all covered; only the sibling-differentiation guidance is missing.

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 every parameter (including the months default of 12) is already documented in the schema. The description restates the formula inputs conceptually but adds no format, unit, or edge-case nuance beyond the schema, so the baseline of 3 applies.

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 (compares), the two resources (annual dorm cost vs. apartment), and the exact formula components feeding the comparison. It also specifies the return content (both totals, the difference, which is cheaper), so an agent can distinguish it from siblings like calculate_rent_vs_buy or calculate_affordability.

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?

Explicitly says to use it 'when a student compares annual dorm cost with renting an apartment,' which gives a clear triggering context. It does not name or exclude the nearest alternative (calculate_rent_vs_buy / calculate_lease_vs_buy), so the agent must infer the boundary itself.

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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