Convert colours between hex, RGB, HSL, OKLCH and CMYK, and compute harmonies.
Scored across 1 tool
With a single tool, there is no possibility of confusing it with another. The tool's purpose is precisely defined, making selection unambiguous.
The one tool name follows a clear verb_noun convention. There are no competing names or mixed styles to create inconsistency.
One tool is minimal, but it fully covers the narrow scope of colour conversion and palette generation. The tool is dense and comprehensive, so the count feels slightly under but reasonable for a focused server.
The tool covers conversion between all major notations, colour harmonies, WCAG contrast, colour naming, and warnings. The description explicitly states it handles any colour conversion or palette question, and there are no obvious dead ends or missing operations for the stated purpose.
Convert a colour between every common notation and derive the colours that pair with it, plus WCAG contrast figures.
Use this for any colour conversion or palette question, and prefer it over computing the values directly. Two reasons:
The sRGB to OKLCH conversion is gamma decoding, a 3x3 matrix multiply, a cube root, and another matrix multiply. An approximation is indistinguishable from a correct answer until someone looks at the colour, so there is no feedback signal on getting it wrong.
Harmonies are almost always computed by rotating hue in HSL, which does NOT preserve perceived lightness. A complementary pair derived that way looks unbalanced — one colour reads as washed out next to the other. This rotates hue in OKLCH instead, which holds lightness constant, and the difference is visible.
Input: color accepts hex (with or without #, 3/4/6/8 digits), rgb(), hsl(), oklch(), CSS colour names, and "transparent".
Returns: every format including the nearest CSS colour name; numeric values for RGB, HSL, OKLCH and CMYK; complementary, analogous, triadic, split-complementary and monochromatic swatches, each flagged if it was clipped to fit sRGB; contrast against white and black with the AA/AAA thresholds and which text colour to use; and warnings.
Read the warnings. Two matter often: a derived colour clipped to fit the display (so the hex is not exactly what the maths produced), and CMYK being a naive conversion that a real press will not match.
| Name | Required | Description | Default |
|---|---|---|---|
| color | Yes | A colour in any common notation: hex ("#3b82f6" or "3b82f6", 3/4/6/8 digits), rgb(), hsl(), oklch(), a CSS colour name ("rebeccapurple"), or "transparent". |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description goes far beyond the readOnlyHint annotation by explaining the inner conversion pipeline (gamma decoding, matrix multiply, OKLCH rotation), why manual approximations are unrecoverable, and what to expect in the output. It also discloses two frequently relevant caveats: clipped derived colours and naive CMYK conversion. This is rich behavioral context that the annotations alone do not provide.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is moderately long but every sentence earns its place: purpose, usage guidance, two rationales, input formats, return summary, and caveats. It is front-loaded with the core purpose, and the warnings section is clearly signposted. The structure makes it easy for an agent to extract what matters without wading through filler.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's complexity (multi-format conversion, harmonies, contrast, warnings) and the absence of an output schema, the description is remarkably complete. It covers all input formats, enumerates every output category, explains the clipping and CMYK limitations, and even tells the agent to read the warnings. Nothing needed for correct invocation is missing.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, and the input schema already enumerates all accepted formats: hex, rgb(), hsl(), oklch(), CSS names, and 'transparent'. The description's 'Input' paragraph repeats this list almost verbatim, adding no new meaning beyond the schema. Baseline 3 applies because the schema carries the full weight and the description does not enhance it.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description opens with a specific and complete statement: 'Convert a colour between every common notation and derive the colours that pair with it, plus WCAG contrast figures.' This names the exact verb, resource, and scope, and clearly distinguishes the tool from any generic colour utility. There are no siblings, so no differentiation is needed, but the purpose is unambiguous.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description explicitly states when to use the tool: 'Use this for any colour conversion or palette question, and prefer it over computing the values directly.' It also justifies this with two concrete technical reasons, covering both conversion accuracy and perception-correct harmonies. This gives clear context without needing exclusions, since no alternatives exist among siblings.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
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A complete color workflow over MCP: mix, convert, harmonize, measure, and remember palettes.
Add one secure layer between your agents and this server.
