Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/JansenAnalytics/claudexnpx agentmods add skills/jansenanalytics/claudex/responsive-checkerWrote 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.
[](https://agentmods.dev/skills/jansenanalytics/claudex/responsive-checker)<a href="https://agentmods.dev/skills/jansenanalytics/claudex/responsive-checker"><img src="https://agentmods.dev/badge/skills/jansenanalytics/claudex/responsive-checker.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00030 | $0.00661 |
| Opus 5 | $0.00015 | $0.00331 |
| Sonnet 5 | $0.00006 | $0.00132 |
| Haiku 4.5 | $0.00003 | $0.00066 |
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 4d 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.
How it starts
The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.
responsive-checker
Test responsive design across viewport sizes: capture screenshots at mobile/tablet/desktop breakpoints, detect overflow issues, flag breakpoint problems.
When to Use
- Verifying responsive layouts after CSS changes
- Testing mobile views of new pages
- Checking that components adapt properly across breakpoints
- Auditing responsive CSS for gaps or inconsistencies
- Detecting overflow issues at specific viewport sizes
Scripts
responsive-capture.py
Captures screenshots at multiple viewport sizes using Chromium.
python3 scripts/responsive-capture.py \
--url https://example.com \
--output-dir ./captures
Or with a local HTML file:
python3 scripts/responsive-capture.py \
--url file:///path/to/page.html \
--output-dir ./captures \
--sizes "375x667,768x1024,1440x900"
Arguments:
--url— URL or file:// path to capture (required)--output-dir— Directory for output screenshots (default:./responsive-captures)--sizes— Comma-separated viewport sizes (default:375x667,768x1024,1440x900,1920x1080)--delay— Seconds to wait after page load before capture (default: 2)
Default breakpoints:
- Mobile: 375×667
- Tablet: 768×1024
- Desktop: 1440×900
- Wide: 1920×1080
overflow-detector.py
Detects responsive issues by injecting JavaScript checks at various viewport sizes.
python3 scripts/overflow-detector.py \
--url https://example.com \
--output report.json
Arguments:
--url— URL to analyze (required)--output— JSON report path (default: stdout)--sizes— Viewport sizes to check (default:375x667,768x1024,1440x900)
Detects:
- Horizontal overflow (elements wider than viewport)
- Text truncation without ellipsis
- Non-responsive images (fixed width > viewport)
- Touch targets too small (<44px on mobile sizes)
breakpoint-analyzer.sh
Static analysis of CSS files for media query patterns.
bash scripts/breakpoint-analyzer.sh style.css [additional.css ...]
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.
- 4d ago First seen · 102 lines · 30 tokens per session scan A e6c1467fe1ef
responsive-checker is a skill published in the GitHub repository JansenAnalytics/claudex (5 stars, last pushed 2mo ago), licensed MIT. It adds 30 tokens to every session and 661 once invoked, about $0.0002 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 2026-09-03.
Other skills, from other repositories
responsive-patterns
Responsive design with Container Queries, fluid typography, cqi/cqb units, subgrid, intrinsic layouts, foldable devices, and mobile-first patterns for React applications. Use when building responsive layouts or container queries.
compatibility-testing
Cross-browser, cross-platform, and cross-device compatibility testing ensuring consistent experience across environments. Use when validating browser support, testing responsive design, or ensuring platform compatibility.
visual-testing-advanced
Advanced visual regression testing with pixel-perfect comparison, AI-powered diff analysis, responsive design validation, and cross-browser visual consistency. Use when detecting UI regressions, validating designs, or ensuring visual consistency.
responsive-design
Mobile-first responsive design covering fluid layouts, media queries, flexbox, grid, viewport units, and responsive images.
image-compare
Compare two image files on disk and report what changed, region by region. Trigger on "what changed between these two images", "diff these PNGs", "did this render drift", "compare screenshots/exports/renders".
Cypress v14 Component Testing
Component testing patterns with Cypress v14 including React, Vue, and Angular component mounting, custom mount commands, interaction testing, visual snapshots, and integration with Vite and Webpack bundlers.