Changelog

All notable changes to this project are documented here. The format follows Keep a Changelog and the project uses Semantic Versioning.

[Unreleased]

[2.0.0] - 2026-11-14

Breaking release: HCT-based outputs, gradient steps semantics, tool error handling and input limits changed — see Changed.

Added

• audit_design_md tool: audits the color tokens of a DESIGN.md file (YAML front matter and fenced yaml blocks). It checks WCAG and APCA contrast for pairs declared in components and pairs inferred from token names, color-blind collisions between accent and status colors, exact and near-duplicate tokens, disliked colors, broken {colors.x} references and a missing primary. Failing pairs get a same-hue fix. Values it cannot evaluate (hwb(), lab(), lch(), color-mix(), transparent) are listed, never guessed.

• export_palette format design-md: a colors: block for DESIGN.md front matter.

• Agent-oriented tools: describe_color, fix_contrast, design_ui_palette, audit_ui_colors and generate_categorical_palette.

• Color input now accepts CSS named colors, CSS Color 4 rgb()/hsl() syntax (space-separated, decimals, percentages, alpha), oklch(), oklab(), hct() and bare 6/8-digit hex. convert_color can output oklab and oklch.

• MCP tool annotations on every tool (readOnlyHint, destructiveHint: false, openWorldHint: false).

• CHANGELOG.md.

• MCP catalog metadata:

  • server.json for the official MCP Registry, under the name io.github.x51xxx/coolors-mcp with schema 2025-12-11;
  • the matching mcpName in package.json;
  • glama.json for Glama.

  After the npm publish, the release workflow publishes to the registry through GitHub OIDC using a signature-verified mcp-publisher.

Changed

• HCT is now Google's CAM16-based HCT, provided by @material/material-color-utilities (pinned to ^0.3.0, because 0.4.0 fails to load in plain Node ESM). The old implementation was CIE LCh with clipping, so tones drifted by up to 20 L* and Material themes failed contrast. Every HCT-based output changes: Material themes, tonal palettes and scales, state colors, semantic palettes, harmonization, dislike detection, image theming and convert_color to hct.
• Material core palettes use Material's fixed chromas: secondary 16, tertiary 24, neutral 4, neutral-variant 8, error at hue 25 / chroma 84.
• generate_gradient: steps is now the total number of colors, and every input color is kept as a stop. steps smaller than the number of colors is an error.
• Tool errors (invalid input, failed validation, exceptions) are returned as MCP tool results with isError: true, so the calling model can read them and retry. Tool execute functions now throw ToolInputError instead of returning error strings.
• JSON Schemas are generated in zod input mode: parameters that have defaults are no longer listed as required.
• Server instructions are now sent to clients.
• Inputs are bounded:
  • most color arrays are capped at 64–256 entries;
  • themeCSS is limited to 200k characters and css to 500k;
  • images are limited to 256×256 RGBA, and data must equal width × height × 4;
  • check_palette_accessibility lists at most 20 collisions per CVD type.
• Color-vision simulation:
  • the anomalous trichromacies use Machado et al. severity 0.6 matrices;
  • achromatopsia maps to a grey of equal relative luminance.
• Package and CI:
  • engines.node >= 20;
  • the published files are whitelisted to dist, README.md and LICENSE;
  • failing tests now fail CI and release.

Fixed

• refactor_css_with_theme corrupted CSS when a line held two or more colors, and rewrote colors inside url(), strings and comments. It now rewrites only real declaration values, skipping selectors and custom-property definitions, and detects the property per declaration.
• The theme parser and matcher read rgb() channels as 0–1, so rgb() colors never matched. They now use the shared color parser.
• Invalid hex (#ggg, #ff00zz, #12345) was silently parsed as another color. It is now rejected. Out-of-range rgb() channels are clamped as in CSS.
• APCA light-on-dark exponents were swapped. Results now match apca-w3 0.1.9 exactly.
• lighten, darken, saturate and desaturate ignored fractional amounts and changed the color at amount 0.
• generate_palette_with_locks:
  • gradient mode returned locked colors first and the wrong count;
  • harmony mode could return fewer colors than requested.
• harmonize_colors ignored factor: 0.
• generate_theme_css with custom includeTones referenced CSS variables it never defined.
• generate_theme_from_image silently fell back to #4285F4 with "NaN%" for images without colorful pixels. It now returns an error, and extract_image_colors reports the real dominant colors instead.
• export_palette:
  • an unsafe prefix produced invalid output;
  • non-ASCII names became ---n-code;
  • names that collided after normalization were silently merged.
• The theme parser dropped a custom property without a trailing ; (:root { --a: #fff }, valid CSS) and failed on comments inside values.
• generate_theme_from_image showed 0% coverage for a seed adjusted away from a disliked color, and ignored includeCustomColors.
• generate_tonal_scale used name verbatim, so "Brand Blue" produced the invalid custom property --brand blue-500; names are now slugified.
• harmonize_colors (harmonize) mishandled hues on either side of 0°/360° (full 15° rotation in the wrong direction); it now matches Material's Blend.harmonize exactly.
• Theme match confidence could exceed 100%.
• match_theme_color reported invalid colors as "no match", and theme CSS without color variables is now an error.
• package.json main pointed to a missing file, and the jsr.json export path was wrong.

Security

• Removed unused runtime dependencies file-type, fuse.js, mcp-proxy, undici and uri-templates, and updated @modelcontextprotocol/sdk to ^1.32.2 and zod to ^4.6.7. Production audit advisories dropped from 113 to 51. The remaining advisories are in the SDK's HTTP transport stack, which the stdio server does not import.
• The development CLI no longer runs commands through a shell with interpolated file paths.

[1.1.0]

• Visual cohesion tools, color-vision-deficiency simulation, APCA contrast, and fixes to tool schemas and RGB conversion.