EveryCalc

calculate_unit_converter

Read-onlyIdempotent

Converts a value between units in one category: length, weight, temperature, volume, or speed. Returns the converted result in the page's display precision, the value in base units, and the conversion rate (null for temperature, which uses an offset scale). Unit codes must belong to the chosen category. Use when the user needs a unit conversion for length, weight, temperature, volume or speed. 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 unit converter calculator.

Input Schema

Name	Required	Description
`value`	Yes	Value to convert.
`to_unit`	No	Unit code to convert to. Must be a unit of the chosen category, using the same code lists as from_unit.
`category`	No	Unit category to convert within.
`from_unit`	No	Unit code to convert from. Must be a unit of the chosen category: length m, km, cm, mi, ft, in; weight kg, g, lb, oz; temperature C, F, K; volume L, mL, gal, floz; speed ms, kmh, mph.

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

A4/5.0

Behavior4/5

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

Goes beyond the readOnly/idempotent annotations by disclosing the return payload shape (page display precision, base-unit value, conversion rate) and the notable quirk that temperature's rate is null because it uses an offset scale. It also mandates surfacing calculator_url as a markdown link, a behavioral requirement annotations cannot express.

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

Conciseness3/5

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

Front-loads the core operation well, but the category list ('length, weight, temperature, volume, or speed') is repeated verbatim in the usage sentence, and the IMPORTANT block is verbose. Some sentences do not fully earn their place.

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 an output schema present, return-value details need not be repeated, and the description still adds the temperature null-rate quirk and the link-rendering requirement. Annotations cover the safety profile, so an agent has everything needed to call this correctly.

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 coverage is 100% with enums and per-parameter descriptions, so the schema carries the load. The description adds only the constraint that unit codes must belong to the chosen category, which is already in the schema text, making it a baseline 3.

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 (converts) and resource (value between units) with the enumerated categories, so the agent immediately knows the operation. No sibling tool overlaps with unit conversion, so no differentiation is needed.

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 'Use when the user needs a unit conversion for length, weight, temperature, volume or speed,' giving a clear trigger condition. It offers no exclusions or alternatives, but none of the siblings compete for the same request.

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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