Hopi

Data size converter

hopi_data_size_converter

Read-onlyIdempotent

Convert a digital storage size between units. Units: B (bytes), KB, MB, GB, TB. By default 1 KB = 1000 bytes (decimal, as storage is sold). Set binary to true for 1 KB = 1024 bytes (as Windows reports drive sizes). Source: https://hopi.co.uk/data-size-converter/

Input Schema

TableJSON Schema

Name	Required	Description
`to`	Yes	Unit to convert to
`from`	Yes	Unit to convert from
`value`	Yes	The size value to convert
`binary`	No	Use binary units (1 KB = 1024 bytes) instead of decimal (default false)

Output Schema

TableJSON Schema

Name	Required	Description
`to`	Yes
`from`	Yes
`value`	Yes
`binary`	Yes
`result`	Yes
`summary`	Yes
`source_url`	Yes	The tool's page on hopi.co.uk (cite or open to check the figure)

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 20, 2026

addedOutput schema / required

Added value: +[
+  "binary",
+  "from",
+  "result",
+  "source_url",
+  "summary",
+  "to",
+  "value"
+]

First observedSep 20, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds behavioral nuance about decimal vs binary conversion and the real-world rationale (storage sold vs Windows), which goes beyond the schema. It doesn't contradict any annotation.

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 concise sentences plus a source link. The main purpose is front-loaded, the units are listed, and the binary/decimal explanation is compact and directly relevant. No filler or redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple converter with a fully described schema, an output schema, and annotations covering safety and idempotency, the description is complete. It explains the units, the decimal/binary distinction, and provides a source, leaving no ambiguity for an agent to call it correctly.

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 all parameters are documented. The description enriches the binary parameter by explaining 'as storage is sold' and 'as Windows reports drive sizes', giving practical meaning beyond the schema's technical description. This adds value without redundancy.

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 clearly states the verb 'convert' and the specific resource 'digital storage size between units', listing the exact units (B, KB, MB, GB, TB). This distinguishes it from other converter tools like length or weight converters, and the mention of decimal vs binary adds further specificity.

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 provides clear usage context by explaining when to use decimal (storage as sold) vs binary (Windows drive sizes), which is critical for correct conversion. It doesn't explicitly name alternatives, but the units and context make it obvious this is for digital storage, not other measurements.

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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