web-perf

web-perf is a skill for Claude Code from solo-super/marketplace. It costs 96 tokens per session (2,051 once invoked), scanned A, a copy of web-perf, MIT.

A web-performance audit skill that uses Chrome DevTools to inspect loading, responsiveness, layout movement, caching, and accessibility. Core Web Vitals are Google’s measures of real-world page loading, interaction, and visual stability.

In plain words
What is it for?
Use it to audit or debug a website’s performance, measure metrics such as LCP, INP, and CLS, inspect network dependencies, and identify render-blocking resources.
Why use it?
It turns browser measurements and traces into specific causes of slow pages, delayed interactions, layout shifts, and related issues.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the web-superpowers plugin — 3 skills shipped together

Good fit Use it to audit or debug a website’s performance, measure metrics such as LCP, INP, and CLS, inspect network dependencies, and identify render-blocking resources.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/solo-super/marketplace/web-perf
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 solo-super/marketplace --skill web-perf
Clone the repo
git clone --depth 1 https://github.com/solo-super/marketplace

Made for: Claude Code.

Or install web-superpowers, the plugin that ships this one along with the rest of its 3 skills.

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-perf

README.md
[![agentmods](https://agentmods.dev/badge/skills/solo-super/marketplace/web-perf/github.svg)](https://agentmods.dev/skills/solo-super/marketplace/web-perf)
Your own site
<a href="https://agentmods.dev/skills/solo-super/marketplace/web-perf"><img src="https://agentmods.dev/badge/skills/solo-super/marketplace/web-perf/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-perf

Your own site · 80×15
<a href="https://agentmods.dev/skills/solo-super/marketplace/web-perf"><img src="https://agentmods.dev/badge/skills/solo-super/marketplace/web-perf.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 96 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,051 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 100% 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 5.1 $0.00096 $0.02051
Opus 5 $0.00048 $0.01026
Sonnet 5 $0.00019 $0.00410
Haiku 4.5 $0.00010 $0.00205

Measured 8d ago against content hash 94c5cb377666, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

web-perf 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 8d 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

100% identical to web-perf — 10 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.

plugins/web-superpowers/skills/web-perf/SKILL.md · 202 lines

How it starts

The opening of the file, as written. The whole thing — 202 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Web Performance Audit

Your knowledge of web performance metrics, thresholds, and tooling APIs may be outdated. Prefer retrieval over pre-training when citing specific numbers or recommendations.

Retrieval Sources

Source How to retrieve Use for
web.dev https://web.dev/articles/vitals Core Web Vitals thresholds, definitions
Chrome DevTools docs https://developer.chrome.com/docs/devtools/performance Tooling APIs, trace analysis
Lighthouse scoring https://developer.chrome.com/docs/lighthouse/performance/performance-scoring Score weights, metric thresholds

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)

Read the full file on GitHub · 202 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. 8d ago First seen · 202 lines · 96 tokens per session scan A 94c5cb377666

Subscribe to this mod's changes

web-perf is a skill published in the GitHub repository solo-super/marketplace (2 stars, last pushed 1mo ago), licensed MIT. It adds 96 tokens to every session and 2,051 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to web-perf, differing in 10 lines, and is treated as a copy.

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