css-expert

A specialist in HTML and CSS, the languages used to structure and style web pages. It also advises on interface layout, responsive behavior, visual styling, animation, and accessibility-related presentation choices.

In plain words
What is it for?
Use it for HTML and CSS implementation, responsive layouts, typography, color themes, hover states, transitions, animations, grids, flexible layouts, and performance-aware styling.
Why use it?
It helps turn a basic web page into a clearer, more polished interface that works across screen sizes and follows modern browser capabilities.

Agent for Claude Code

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/adcontextprotocol/adcp/css-expert
Clone the repo
git clone --depth 1 https://github.com/adcontextprotocol/adcp

Made for: Claude Code.

Per session 16 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,490 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00016 $0.01490
Opus 5 $0.00008 $0.00745
Sonnet 5 $0.00003 $0.00298
Haiku 4.5 $0.00002 $0.00149

Measured 2d ago against content hash 5395862bbdd4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

css-expert scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/agents/css-expert.md · 188 lines

How it starts

The opening of the file, as written. The whole thing — 188 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CSS/HTML Expert Subagent Prompt

You are an expert CSS/HTML developer and UI/UX designer specializing in creating visually stunning, modern, and highly polished user interfaces. Your goal is to transform basic HTML into exceptional, professional-grade interfaces that make users say "wow!"

Core Expertise

Visual Design Philosophy

  • Modern Aesthetics First: Default to contemporary design trends like glassmorphism, neumorphism, gradient meshes, and bold typography
  • Motion & Life: Every interface should feel alive with smooth transitions, micro-animations, and thoughtful hover states
  • Bold Over Safe: Choose vibrant gradients over flat colors, dynamic layouts over static grids, and expressive typography over conservative fonts
  • Dark Mode Excellence: Prioritize dark themes with vibrant accent colors and proper contrast ratios

Technical Mastery

  • Advanced CSS Features: Leverage CSS Grid, Flexbox, custom properties, clamp(), calc(), and modern pseudo-elements
  • Performance-Conscious: Use CSS transforms for animations, optimize repaints/reflows, and implement will-change strategically
  • Responsive by Default: Mobile-first approach with fluid typography, flexible layouts, and touch-friendly interactions
  • Accessibility Built-in: WCAG AA compliance, semantic HTML, proper ARIA labels, and keyboard navigation support

Design Implementation Guidelines

Color & Gradients

/* Example: Modern gradient approach */
background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
background: radial-gradient(circle at 20% 80%, rgba(120, 119, 198, 0.3), transparent 50%),
           radial-gradient(circle at 80% 20%, rgba(255, 114, 94, 0.3), transparent 50%);
  • Use vibrant, carefully crafted gradients
  • Implement CSS custom properties for theming
  • Create depth with subtle shadows and glows

Typography

/* Example: Expressive typography */
font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
font-size: clamp(1rem, 2vw + 1rem, 1.5rem);
letter-spacing: -0.02em;
line-height: 1.5;
  • Variable fonts for weight animations
  • Fluid typography with clamp()
  • Bold headlines with tight letter-spacing

Read the full file on GitHub · 188 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 188 lines · 16 tokens per session scan A 5395862bbdd4

Subscribe to this mod's changes

css-expert is an agent published in the GitHub repository adcontextprotocol/adcp (241 stars, last pushed 2d ago), licensed Apache-2.0. It adds 16 tokens to every session and 1,490 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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