Hopi

Random colour generator

hopi_random_colour_generator

Read-onlyIdempotent

Generate a random colour and return its hex, RGB and HSL values. Each of the red, green and blue channels gets an independent value from 0 to 255. Source: https://hopi.co.uk/random-colour-generator/

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description
`hex`	No
`hsl`	No
`rgb`	No
`summary`	Yes
`hslString`	No
`rgbString`	No
`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: +[
+  "source_url",
+  "summary"
+]
```
First observedSep 20, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already cover read-only, non-destructive, and idempotent behaviour. The description adds useful behavioral detail beyond those annotations: each RGB channel is independently drawn from 0 to 255, making the randomness model explicit. 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?

Two sentences carry all essential information: the core action and output formats, followed by a precise behavioural detail about channel independence. The source link is non-essential but harmless; there is no filler.

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 zero-parameter, read-only utility with an output schema and safety annotations, the description is fully sufficient. It states what the tool returns, how the random values are generated, and leaves no prerequisites, options, or hidden behaviours unexplained.

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 input schema has zero parameters and 100% schema coverage, so there are no parameter semantics for the description to clarify. The baseline for a no-parameter tool is 4, and the description appropriately focuses on the output semantics instead.

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 action ('Generate a random colour') and the exact resource and outputs (hex, RGB, HSL). Among the many colour-related siblings, this unambiguously identifies a standalone random colour generator rather than a palette, shades, or colour-name tool.

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?

There is no explicit when-to-use guidance or named alternatives. However, the zero-parameter signature and clear purpose imply that this tool is for generating a single random colour, so usage is reasonably inferable even without exclusionary language.

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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