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ContrastKit

by contrastkit.mike-tusa.workers.dev · remote · no sign-in to list tools · v0.1.0 · published by dev.workers.mike-tusa.contrastkit

WCAG color contrast checks, nearest accessible color, CSS color conversion and palette pair checks.

Changes · 4
CompareRegistry entry

4 tools: 4 change things.

Scanned Oct 22, 2026

1 check matched something in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http contrastkit https://contrastkit.mike-tusa.workers.dev/mcp

Findings

Matches of fixed checks, with the text they matched.

1 warn
  • Warnconvert_color

    The server marks "convert_color" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

    Matched text

    annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The name "convert_color" says "convert": a word for a change.

    What this check looks for

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

4 tools

Changes things 4Claude Code: ask
  • check_contrastCompute the WCAG 2.x contrast ratio between a text (foreground) color and a background color, with pass/fail for AA, AA large text, AAA, AAA large text and non-text UI (3:1).No findings

    Why it is in this group

    • Nothing in its name or description says what it does, so it is counted as a write.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
    Description, as the server wrote it
    Compute the WCAG 2.x contrast ratio between a text (foreground) color and a background color, with pass/fail for AA, AA large text, AAA, AAA large text and non-text UI (3:1). Handles translucent colors. Read-only. Same engine as GET /api/contrast.

    Annotations the server declares

    • title: Check WCAG color contrast
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: false
  • check_paletteContrast ratio for every pair of 2 to 12 colors (up to 66 pairs), highest first, each flagged against the chosen WCAG level.No findings

    Why it is in this group

    • Nothing in its name or description says what it does, so it is counted as a write.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
    Description, as the server wrote it
    Contrast ratio for every pair of 2 to 12 colors (up to 66 pairs), highest first, each flagged against the chosen WCAG level. Use it to see which brand colors can be used together for text. Read-only. Same engine as GET /api/palette.

    Annotations the server declares

    • title: Check a palette
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: false
  • convert_colorConvert a CSS color to hex, rgb() and hsl(), with its relative luminance, its contrast on white and on black, and the better text color (black or white) to put on it.1 finding

    Why it is in this group

    • The name "convert_color" says "convert": a word for a change.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.

    Findings

    • Warn

      The server marks "convert_color" read-only (readOnlyHint: true), and its own name, description or input give the class "write".

      Matched text

      annotations: {"readOnlyHint":true,"destructiveHint":false,"idempotentHint":true,"openWorldHint":false}; The name "convert_color" says "convert": a word for a change.

      What this check looks for
    Description, as the server wrote it
    Convert a CSS color to hex, rgb() and hsl(), with its relative luminance, its contrast on white and on black, and the better text color (black or white) to put on it. Read-only. Same engine as GET /api/convert.

    Annotations the server declares

    • title: Convert a CSS color
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: false
  • suggest_accessible_colorFor a failing color pair, find the closest color (same hue and saturation, lightness changed as little as possible) that meets the chosen WCAG level.No findings

    Why it is in this group

    • Nothing in its name or description says what it does, so it is counted as a write.
    • The server marks it read-only (readOnlyHint: true), but an annotation never lowers a class.
    Description, as the server wrote it
    For a failing color pair, find the closest color (same hue and saturation, lightness changed as little as possible) that meets the chosen WCAG level. Adjust the foreground (default), the background, or both (best first). Read-only. Same engine as GET /api/suggest.

    Annotations the server declares

    • title: Suggest an accessible color
    • readOnlyHint: true
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: false

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 0.1.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http contrastkit https://contrastkit.mike-tusa.workers.dev/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [],
    "ask": [
      "mcp__contrastkit__check_contrast",
      "mcp__contrastkit__suggest_accessible_color",
      "mcp__contrastkit__convert_color",
      "mcp__contrastkit__check_palette"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as contrastkit. Review it before you use it.