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/frontend-inspectorWrote 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/frontend-inspector)<a href="https://agentmods.dev/skills/jansenanalytics/claudex/frontend-inspector"><img src="https://agentmods.dev/badge/skills/jansenanalytics/claudex/frontend-inspector.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 | $0.00036 | $0.00548 |
| Opus 5 | $0.00018 | $0.00274 |
| Sonnet 5 | $0.00007 | $0.00110 |
| Haiku 4.5 | $0.00004 | $0.00055 |
Grade A, and why
frontend-inspector 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 3d 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 — 83 lines — stays where its author put it; the contents beside it link to each section on GitHub.
frontend-inspector
Analyze frontend screenshots using vision model analysis and automated checks: detect layout bugs, alignment issues, overflow, z-index problems, spacing inconsistencies, color contrast issues.
When to Use
- Reviewing UI implementations before presenting to stakeholders
- Checking visual quality of built pages
- Finding CSS bugs from screenshots or source code
- Self-reviewing frontend work before presenting to the user
- Auditing CSS codebases for common anti-patterns
Scripts
analyze-screenshot.sh
Generates a structured vision-model analysis prompt and checklist for a screenshot.
bash scripts/analyze-screenshot.sh screenshot.png
Output: A Markdown document with:
- The image path for vision model input
- Structured analysis categories (Layout, Typography, Color, Components, Responsiveness)
- A checklist template to fill in during review
Use the output as a prompt when analyzing the screenshot with a vision model.
css-issue-detector.py
Static analysis of HTML/CSS files for common issues.
python3 scripts/css-issue-detector.py --input page.html --output report.json
Arguments:
--input— HTML file to analyze (required)--output— JSON report output path (default: stdout)
Detects:
!importantoveruse (>10 occurrences = warning)- Deeply nested selectors (>4 levels)
- Magic numbers (hardcoded px values that could be variables)
- Missing responsive breakpoints (no media queries)
- z-index wars (z-index > 100)
Output: JSON report with issues grouped by category, each with severity (info/warning/error).
layout-checklist.sh
Generates a page-type-specific review checklist.
bash scripts/layout-checklist.sh --type dashboard
Supported types: dashboard, form, landing, table, card-grid
Output: Markdown checklist with type-specific items to verify.
References
references/common-visual-bugs.md— 30+ common frontend visual bugs catalogreferences/vision-prompt-templates.md— Ready-to-use prompts for vision model screenshot analysis
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.
- 3d ago First seen · 83 lines · 36 tokens per session scan A d4566c9eaee2
frontend-inspector is a skill published in the GitHub repository JansenAnalytics/claudex (5 stars, last pushed 2mo ago), licensed MIT. It adds 36 tokens to every session and 548 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.
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