API Tool Calls

Unit Converter

unit_convert

Read-onlyIdempotent

Convert a bounded decimal or fraction quantity between explicit compatible mass, volume, international length, speed or item-count units. Reject incompatible dimensions; no density is inferred.

Input Schema

TableJSON Schema

Name	Required	Description
`to`	Yes	Target unit in the same dimension. International length definitions and US liquid measures are explicit.
`from`	Yes	Explicit source or target unit. mm is millimeters; oz_av is avoirdupois mass; us_fl_oz is volume. US customary volume measures only.
`value`	Yes	Nonnegative decimal (up to 24 digits, effective exponent ±24), fraction (1/2) or mixed fraction (1 1/2). Quantity and integer fraction components ≤10^12; denominator >0; proper fractional part for mixed values.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedOct 5, 2026

changedInput schema / properties / from / description

Previous value: -"Explicit source unit. oz_av is mass; us_fl_oz is volume. US measures only."New value: +"Explicit source or target unit. mm is millimeters; oz_av is avoirdupois mass; us_fl_oz is volume. US customary volume measures only."

changedInput schema / properties / from / enum

Previous value: -[
-  "us_qt",
-  "us_gal",
-  "us_cup",
-  "us_fl_oz",
-  "us_tbsp",
-  "us_tsp",
-  "ml",
-  "l",
-  "oz_av",
-  "lb_av",
-  "g",
-  "kg",
-  "cm",
-  "m",
-  "in",
-  "ft",
-  "yd",
-  "mi",
-  "km",
-  "knot",
-  "mph",
-  "each"
-]New value: +[
+  "us_qt",
+  "us_gal",
+  "us_cup",
+  "us_fl_oz",
+  "us_tbsp",
+  "us_tsp",
+  "ml",
+  "l",
+  "oz_av",
+  "lb_av",
+  "g",
+  "kg",
+  "cm",
+  "mm",
+  "m",
+  "in",
+  "ft",
+  "yd",
+  "mi",
+  "km",
+  "knot",
+  "mph",
+  "each"
+]

changedInput schema / properties / to / description

Previous value: -"Target must share the source dimension: mass, volume, length, speed or count. International length and nautical mile definitions; US liquid measures."New value: +"Target unit in the same dimension. International length definitions and US liquid measures are explicit."

changedInput schema / properties / to / enum

Previous value: -[
-  "us_qt",
-  "us_gal",
-  "us_cup",
-  "us_fl_oz",
-  "us_tbsp",
-  "us_tsp",
-  "ml",
-  "l",
-  "oz_av",
-  "lb_av",
-  "g",
-  "kg",
-  "cm",
-  "m",
-  "in",
-  "ft",
-  "yd",
-  "mi",
-  "km",
-  "knot",
-  "mph",
-  "each"
-]New value: +[
+  "us_qt",
+  "us_gal",
+  "us_cup",
+  "us_fl_oz",
+  "us_tbsp",
+  "us_tsp",
+  "ml",
+  "l",
+  "oz_av",
+  "lb_av",
+  "g",
+  "kg",
+  "cm",
+  "mm",
+  "m",
+  "in",
+  "ft",
+  "yd",
+  "mi",
+  "km",
+  "knot",
+  "mph",
+  "each"
+]

AddedOct 4, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior, so the bar is low. The description adds genuine behavioral detail beyond them: incompatible dimension pairs are rejected rather than coerced, and no density is synthesized across mass/volume.

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, no filler, with the core capability and the key constraint (no density inference) front-loaded ahead of any caveat.

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?

An output schema exists, so return-format explanation is rightly omitted. Description covers scope, dimension rules, and the density boundary; only the naming of the sibling to use instead is left implicit, a minor gap for a tool with rich structured fields.

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

Parameters4/5

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

Schema coverage is 100%, so baseline is 3. The description still adds value the enums lack by grouping units into dimension families (mass, volume, length, speed, item-count) and by characterizing the value as bounded, which tells the agent the accepted conversion space without scanning 23 enum members.

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 (Convert), the accepted quantity formats (decimal or fraction), and the exact unit families (mass, volume, international length, speed, item-count). 'Reject incompatible dimensions; no density is inferred' cleanly separates it from the sibling mass_volume_convert, which is the obvious confusion point.

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 gives clear selection context: use only for units within the same dimension, and it flags the density boundary that routes mass↔volume work elsewhere. It never names mass_volume_convert as an alternative, so the routing is implicit rather than explicit.

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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