API Tool Calls

Unit Price Calculator

unit_price

Read-onlyIdempotent

Compare package prices per equal mass, volume or whole item count in one entered currency, with exact tie detection and compatible units only.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "currency": "USD",
      "packages": [
        {
          "unit": "g",
          "price": "3",
          "quantity": "500"
        },
        {
          "unit": "kg",
          "price": "5",
          "quantity": "1"
        }
      ],
      "targetUnit": "g"
    },
    "name": "unit_price"
  }
}

Input Schema

Name	Required	Description
`currency`	Yes	Entered three-letter currency label (letters only), shared by all prices; no exchange rates.
`packages`	Yes
`targetUnit`	Yes	One common mass, volume or count unit for comparison.

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 4, 2026

TDQS

A3.8/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, closed-world, and non-destructive, so the safety profile is covered. The description adds real behavior beyond that: exact tie detection and enforcement of compatible units only, plus the single-currency (no FX) constraint.

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?

A single dense sentence with the core action front-loaded and no filler. Every clause (equal mass/volume/count, one currency, tie detection, compatible units) carries distinct information.

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 values need no explanation, and annotations cover the safety profile. The description is nearly complete, missing only minor practical notes such as the minimum of two packages or guidance on what happens with incompatible units.

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 67% and the enum fields and nested package properties are already documented in the schema. The description reinforces that targetUnit is one common mass/volume/count unit and that packages must share a dimension, but adds no syntax or format detail beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb-plus-resource: comparing package prices normalized per equal mass, volume, or item count. This implicitly separates it from raw-conversion siblings like unit_convert and mass_volume_convert, but it never names an alternative, so it stops short of an explicit sibling distinction.

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

Usage Guidelines3/5

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

The scope constraints ('in one entered currency', 'compatible units only') imply when the tool fits, but there is no stated when-to-use/when-not guidance and no alternative tool named for the case where units are incompatible or currencies differ.

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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