web-performance-reviewer

web-performance-reviewer is a skill for Claude Code from AdamBien/airails. It costs 193 tokens per session (2,067 once invoked), scanned A, original, MIT.

A browser-based review helper for measuring web frontend performance with Chrome DevTools. It checks loading behavior, Core Web Vitals, network requests, and memory use in rendered sites.

In plain words
What is it for?
Use it to investigate a slow website or review changes involving images, fonts, or JavaScript. It produces a prioritized report and requires the Chrome DevTools tools to be available.
Why use it?
It finds runtime performance problems that source-code inspection alone cannot reliably measure. The results are lab measurements from one browser and machine, not guarantees about every user's experience.

Skill for Claude Code

Written for Claude Code: argument-hint in frontmatter.

Good fit Use it to investigate a slow website or review changes involving images, fonts, or JavaScript. It produces a prioritized report and requires the Chrome DevTools tools to be available.

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Install with agentmods
npx agentmods add skills/adambien/airails/web-performance-reviewer
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.

Any agent
npx skills add AdamBien/airails --skill web-performance-reviewer
Clone the repo
git clone --depth 1 https://github.com/AdamBien/airails

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 web-performance-reviewer

README.md
[![agentmods](https://agentmods.dev/badge/skills/adambien/airails/web-performance-reviewer/github.svg)](https://agentmods.dev/skills/adambien/airails/web-performance-reviewer)
Your own site
<a href="https://agentmods.dev/skills/adambien/airails/web-performance-reviewer"><img src="https://agentmods.dev/badge/skills/adambien/airails/web-performance-reviewer/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 web-performance-reviewer

Your own site · 80×15
<a href="https://agentmods.dev/skills/adambien/airails/web-performance-reviewer"><img src="https://agentmods.dev/badge/skills/adambien/airails/web-performance-reviewer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 193 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,067 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. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Anti-Refusal · line 10
    Skill instructs the agent to omit warnings, disclaimers, or ethical commentary. Stripping safety caveats hides risk from the user and is a common jailbreak preamble.
    Fix: Remove instructions that suppress warnings, disclaimers, or ethical commentary. Let the agent surface safety-relevant caveats to the user.
How audits are shown
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 $0.00193 $0.02067
Opus 5 $0.00097 $0.01033
Sonnet 5 $0.00039 $0.00413
Haiku 4.5 $0.00019 $0.00207

Measured 9d ago against content hash 0447680006f3, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

web-performance-reviewer 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 9d 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.

web/web-performance-reviewer/SKILL.md · 164 lines

How it starts

The opening of the file, as written. The whole thing — 164 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Review the runtime performance of $ARGUMENTS by measuring the rendered site in a real browser through the Chrome DevTools MCP tools (chrome-devtools). Produce a prioritized, evidence-backed report. If the chrome-devtools MCP tools are unavailable, report the review as not runnable — do not judge performance from source code alone.

Composition

Composes on top of /web-static, /web-sprinkles, or /web-components (and their shared /web-conventions). This skill is a reviewer, not a builder: it measures and prioritizes; fixing belongs to the composed stack skill, and re-verification after a fix belongs to that stack's own loop.

Never part of green. The /web-static verification loop stays fast and deterministic; performance numbers are slow to gather and jitter run-to-run, which makes them a bad gate. This review runs only on explicit request — before publishing, after adding images/fonts/JS, or when something feels slow. A red finding here never turns the composed stack's green red.

Philosophy

  • Lab, not field — everything measured here is lab data from one Chrome on one machine; useful for finding problems and comparing before/after, never a claim about real-user metrics
  • Unthrottled localhost lies — a site served by zws on localhost loads in milliseconds regardless of how bloated it is; only throttled runs reveal what users on mid-range phones see
  • Numbers jitter — a single trace is an anecdote; conclusions come from the median of repeated runs, and high variance is itself a finding to report
  • The trace is the oracle — never diagnose from reading source; the trace, the waterfall, and the heap snapshot are the evidence, source reading only explains what they found
  • If it is fast, say so — do not invent issues; a clean report is a valid outcome

Serve

Serve the site root with zws exactly as the composed stack prescribes: java zws <site-root> (or the copy bundled with web-conventions: java <web-conventions skill dir>/scripts/zws <site-root>). Never use --live during measurement — the injected reload script and its SSE stream would appear in every trace and waterfall and contaminate the evidence. Measure against a plain instance.

Read the full file on GitHub · 164 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 9d ago First seen · 164 lines · 193 tokens per session scan A 0447680006f3

Subscribe to this mod's changes

web-performance-reviewer is a skill published in the GitHub repository AdamBien/airails (49 stars, last pushed yesterday), licensed MIT. It adds 193 tokens to every session and 2,067 once invoked, about $0.0010 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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