web-performance-audit

web-performance-audit is a skill for Claude Code, Codex from warpdotdev/oz-skills. It costs 37 tokens per session (1,898 once invoked), scanned A, a copy of web-perf, MIT.

A website speed audit using Chrome DevTools, a browser toolkit for examining loading, network activity, and page behaviour.

In plain words
What is it for?
Use it to profile page loads, inspect network requests, investigate performance problems, and prioritise fixes based on their likely impact.
Why use it?
It identifies concrete causes of slow loading and checks important user-facing measures such as Core Web Vitals.

Skill for Claude CodeCodex

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 skills/warpdotdev/oz-skills/web-performance-audit
Any agent
npx skills add warpdotdev/oz-skills --skill web-performance-audit
Clone the repo
git clone --depth 1 https://github.com/warpdotdev/oz-skills

Made for: Claude Code, Codex.

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-audit

README.md
[![agentmods](https://agentmods.dev/badge/skills/warpdotdev/oz-skills/web-performance-audit.svg)](https://agentmods.dev/skills/warpdotdev/oz-skills/web-performance-audit)
Your own site
<a href="https://agentmods.dev/skills/warpdotdev/oz-skills/web-performance-audit"><img src="https://agentmods.dev/badge/skills/warpdotdev/oz-skills/web-performance-audit.svg" alt="Measured on agentmods" height="20"></a>
Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,898 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 84% copy Near-identical to another mod 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 $0.00037 $0.01898
Opus 5 $0.00018 $0.00949
Sonnet 5 $0.00007 $0.00380
Haiku 4.5 $0.00004 $0.00190

Measured 4d ago against content hash 2c82ff8d7c14, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

web-performance-audit 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.

Origin

This is a copy

84% identical to web-perf — 15 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/web-performance-audit/SKILL.md · 195 lines

How it starts

The opening of the file, as written. The whole thing — 195 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Web Performance Audit

Audit web page performance using Chrome DevTools MCP tools. This skill focuses on Core Web Vitals, network optimization, and high-level accessibility gaps.

FIRST: Verify MCP Tools Available

Run this before starting. Try calling navigate_page or performance_start_trace. If unavailable, STOP—the chrome-devtools MCP server isn't configured.

Ask the user to add this to their MCP config:

"chrome-devtools": {
  "type": "local",
  "command": ["npx", "-y", "chrome-devtools-mcp@latest"]
}

Key Guidelines

  • Be assertive: Verify claims by checking network requests, DOM, or codebase—then state findings definitively.
  • Verify before recommending: Confirm something is unused before suggesting removal.
  • Quantify impact: Use estimated savings from insights. Don't prioritize changes with 0ms impact.
  • Skip non-issues: If render-blocking resources have 0ms estimated impact, note but don't recommend action.
  • Be specific: Say "compress hero.png (450KB) to WebP" not "optimize images".
  • Prioritize ruthlessly: A site with 200ms LCP and 0 CLS is already excellent—say so.

Quick Reference

Task Tool Call
Load page navigate_page(url: "...")
Start trace performance_start_trace(autoStop: true, reload: true)
Analyze insight performance_analyze_insight(insightSetId: "...", insightName: "...")
List requests list_network_requests(resourceTypes: ["Script", "Stylesheet", ...])
Request details get_network_request(reqid: <id>)
A11y snapshot take_snapshot(verbose: true)

Workflow

Copy this checklist to track progress:

Audit Progress:
- [ ] Phase 1: Performance trace (navigate + record)
- [ ] Phase 2: Core Web Vitals analysis (includes CLS culprits)
- [ ] Phase 3: Network analysis
- [ ] Phase 4: Accessibility snapshot
- [ ] Phase 5: Codebase analysis (skip if third-party site)

Phase 1: Performance Trace

  1. Navigate to the target URL:
    navigate_page(url: "<target-url>")
    

Read the full file on GitHub · 195 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. 4d ago First seen · 195 lines · 37 tokens per session scan A 2c82ff8d7c14

Subscribe to this mod's changes

web-performance-audit is a skill published in the GitHub repository warpdotdev/oz-skills (823 stars, last pushed 19d ago), licensed MIT. It adds 37 tokens to every session and 1,898 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 84% identical to web-perf, differing in 15 lines, and is treated as a copy.

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