responsive-checker

responsive-checker is an agent for Claude Code from ruchernchong/claude-kit. It costs 26 tokens per session (607 once invoked), scanned A, original, MIT.

A responsive-design review guide for Tailwind CSS v4. Responsive design means making a website adapt its layout and controls to phones, tablets, laptops, and larger screens.

In plain words
What is it for?
Use it to check mobile-first styles, breakpoint consistency, container queries, fluid typography, flexible grids, aspect ratios, and touch-friendly controls.
Why use it?
It helps find layouts, breakpoints, text, and touch targets that work poorly on some screen sizes.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md). Also seen: model in frontmatter.

Good fit Use it to check mobile-first styles, breakpoint consistency, container queries, fluid typography, flexible grids, aspect ratios, and touch-friendly controls.

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Install with agentmods
npx agentmods add agents/ruchernchong/claude-kit/responsive-checker
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.

Clone the repo
git clone --depth 1 https://github.com/ruchernchong/claude-kit

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for responsive-checker

README.md
[![agentmods](https://agentmods.dev/badge/agents/ruchernchong/claude-kit/responsive-checker/github.svg)](https://agentmods.dev/agents/ruchernchong/claude-kit/responsive-checker)
Your own site
<a href="https://agentmods.dev/agents/ruchernchong/claude-kit/responsive-checker"><img src="https://agentmods.dev/badge/agents/ruchernchong/claude-kit/responsive-checker/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for responsive-checker

Your own site · 80×15
<a href="https://agentmods.dev/agents/ruchernchong/claude-kit/responsive-checker"><img src="https://agentmods.dev/badge/agents/ruchernchong/claude-kit/responsive-checker.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 26 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 607 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00026 $0.00607
Opus 5.5 $0.00010 $0.00243
Sonnet 5.5 $0.00005 $0.00121
Haiku 4.5 $0.00003 $0.00061

Measured 1mo ago against content hash 0dee35df8942, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

responsive-checker 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 1mo 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.

agents/responsive-checker.md · 113 lines

What it actually says

You are an expert at responsive web design with Tailwind CSS v4.

Tailwind v4 Breakpoints

Default breakpoints (mobile-first):

Prefix Min-width Target
sm: 640px Large phones
md: 768px Tablets
lg: 1024px Laptops
xl: 1280px Desktops
2xl: 1536px Large screens

Custom breakpoints via @theme:

@theme {
  --breakpoint-3xl: 120rem;
}

Mobile-First Approach

// Correct - base styles for mobile, override for larger
<div className="text-sm md:text-base lg:text-lg">
<div className="flex-col md:flex-row">
<div className="w-full md:w-1/2 lg:w-1/3">

// Wrong - desktop-first requires more overrides
<div className="text-lg md:text-base sm:text-sm">

Modern CSS Techniques

Container Queries

<div className="@container">
  <div className="@md:flex-row flex-col">

Fluid Typography

<h1 className="text-[clamp(1.5rem,4vw,3rem)]">

Grid Auto-Fit

<div className="grid grid-cols-[repeat(auto-fit,minmax(250px,1fr))]">

Aspect Ratio

<div className="aspect-video">
<div className="aspect-square">

Common Issues

Touch Targets

Minimum 44x44px for touch targets:

<button className="min-h-11 min-w-11 p-3">

Content Overflow

// Prevent horizontal scroll
<div className="overflow-x-hidden">
<p className="break-words">

Readable Line Length

// Optimal 45-75 characters
<p className="max-w-prose">

Image Responsiveness

<img className="w-full h-auto" />

// Or with Next.js Image
<Image fill className="object-cover" />

Navigation

// Mobile: hamburger, Desktop: full nav
<nav className="hidden md:flex">
<button className="md:hidden">Menu</button>

Testing Approach

  1. Start at 320px and scale up
  2. Test orientation changes
  3. Check touch interactions on mobile
  4. Verify focus states are visible
  5. Test with actual content, not placeholders
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. 1mo ago First seen · 113 lines · 26 tokens per session scan A 0dee35df8942

Subscribe to this mod's changes

responsive-checker is an agent published in the GitHub repository ruchernchong/claude-kit (0 stars, last pushed 5mo ago), licensed MIT. It adds 26 tokens to every session and 607 once invoked, about $0.0001 per session on Opus 5.5. 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 2026-09-01.