Hopi

Aspect ratio calculator

hopi_aspect_ratio_calculator

Read-onlyIdempotent

Aspect ratio helper. In 'simplify' mode, give width and height to get the simplified W:H ratio, decimal ratio and nearest common ratio. In 'solve' mode, give a ratio (ratioW:ratioH) plus one of width or height to get the missing side. Source: https://hopi.co.uk/aspect-ratio-calculator/

Input Schema

TableJSON Schema

Name	Required	Description
`mode`	Yes	'simplify' a width and height, or 'solve' a missing side from a ratio
`width`	No	Width in pixels or units (simplify mode, or the known side in solve mode)
`height`	No	Height in pixels or units (simplify mode, or the known side in solve mode)
`ratioH`	No	Ratio height part, e.g. 9 (solve mode)
`ratioW`	No	Ratio width part, e.g. 16 (solve mode)

Output Schema

TableJSON Schema

Name	Required	Description
`mode`	Yes
`ratio`	Yes
`decimal`	No
`nearest`	No
`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: +[
+  "mode",
+  "ratio",
+  "source_url",
+  "summary"
+]

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 mark the tool as read-only, idempotent and non-destructive, and the description adds useful behavioral context by describing the outputs produced in each mode and including the source URL. There is no contradiction with the annotations.

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?

The description is concise and front-loaded with the tool's purpose, then splits into two clearly labelled modes. Every sentence adds value, and the source URL is placed at the end without cluttering the guidance.

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 stateless calculator with rich schema descriptions, read-only annotations, and an output schema, the description covers all necessary calling information: modes, input requirements, output types, and source. No critical usage detail is missing.

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?

The schema already documents all parameters, but the description adds meaningful mappings for how parameters are used in each mode, including the important detail that solve mode requires ratioW:ratioH plus one of width or height. It also clarifies the intended ratio format. This goes beyond the flat property descriptions.

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 identifies the tool as an aspect ratio helper and immediately explains its two modes: simplify width/height into W:H ratio, decimal ratio and nearest common ratio, or solve for a missing side from a ratio plus one known side. It is specific enough to distinguish this from sibling calculators like hopi_ratio_calculator.

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 explicit mode-based instructions: use 'simplify' with width and height, and use 'solve' with ratioW:ratioH plus one known side. It does not explicitly name alternatives or state when not to use the tool, but the mode guidance is clear and actionable.

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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