Contrast Master

What it does

When your agent uses it

• Tasks that involve Theming and dark mode
• Tasks that involve Accessibility

Example prompts

• “/contrast-master”

Requirements

• Python 3

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

1. 1Check every text-on-background combination in both themes
2. 2Do not assume that inverting colors maintains contrast
3. 3Placeholder text often fails in dark mode (gray on dark gray)
4. 4Borders that were visible on white may disappear on dark backgrounds
5. 5Shadows that provided depth on light mode do nothing on dark mode -- use borders instead
6. 6Test focus indicators in both themes

What it can do on your machine

Read from SKILL.md and the folder at commit decf6ba. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are css and python).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Contrast Master loads about 1.4k tokens when it runs, and up to ~5.3k if it reads all its reference files. Until then it costs about 23 tokens; SKILL.md has 564 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~23

When it runs · the whole SKILL.md, loaded when a task matches

~1.4k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~5.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from Community-Access/accessibility-agents at commit decf6ba, republished under its MIT licence (© Community-Access). 564 words, ~1,449 tokens.

name

contrast-master

description

Color contrast, themes, dark mode, non-text contrast and color-only meaning.

license

MIT

disable-model-invocation

true

metadata.tier

specialist

metadata.domain

web

metadata.output

findings

metadata.effort

medium

metadata.title

Contrast Master

import sys

def luminance(r, g, b):
    vals = []
    for v in [r, g, b]:
        v = v / 255.0
        vals.append(v / 12.92 if v <= 0.04045 else ((v + 0.055) / 1.055) ** 2.4)
    return 0.2126 * vals[0] + 0.7152 * vals[1] + 0.0722 * vals[2]

def contrast(hex1, hex2):
    r1, g1, b1 = int(hex1[1:3],16), int(hex1[3:5],16), int(hex1[5:7],16)
    r2, g2, b2 = int(hex2[1:3],16), int(hex2[3:5],16), int(hex2[5:7],16)
    l1, l2 = luminance(r1,g1,b1), luminance(r2,g2,b2)
    lighter, darker = max(l1,l2), min(l1,l2)
    return (lighter + 0.05) / (darker + 0.05)

fg = sys.argv[1]
bg = sys.argv[2]
ratio = contrast(fg, bg)
status = 'PASS' if ratio >= 4.5 else ('LARGE TEXT ONLY' if ratio >= 3.0 else 'FAIL')
print(f'{ratio:.2f}:1 -- {status}')

:focus-visible {
  outline: 2px solid #005fcc;
  outline-offset: 2px;
}

:focus-visible {
  outline: 2px solid #ffffff;
  box-shadow: 0 0 0 4px #000000;
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

© Community-Access, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 5 other files (references) in skills/contrast-master of Community-Access/accessibility-agents.

• SKILL.md
• agents/openai.yaml
• examples/findings.json
• references/color-independence.md
• references/user-preference-media-queries-prefers.md
• references/validation-checklist.md

Open the folder on GitHubat commit decf6ba