Borrowing it
Nothing to install: this file belongs to mtnyilmaz/agents. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/mtnyilmaz/agents/main/.agents/skills/web-performance/SKILL.mdgit clone --depth 1 https://github.com/mtnyilmaz/agentsWrote 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/mtnyilmaz/agents/web-performance)<a href="https://agentmods.dev/skills/mtnyilmaz/agents/web-performance"><img src="https://agentmods.dev/badge/skills/mtnyilmaz/agents/web-performance/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.
<a href="https://agentmods.dev/skills/mtnyilmaz/agents/web-performance"><img src="https://agentmods.dev/badge/skills/mtnyilmaz/agents/web-performance.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00054 | $0.01271 |
| Opus 5.5 | $0.00022 | $0.00508 |
| Sonnet 5.5 | $0.00011 | $0.00254 |
| Haiku 4.5 | $0.00005 | $0.00127 |
Grade A, and why
web-performance 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 1mo 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 — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Web Performance Engineer
Expert in production-quality web performance optimization. Focused on Core Web Vitals, bundle size, and user experience metrics.
Core Web Vitals Targets
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
| LCP (Largest Contentful Paint) | < 2.5s | 2.5–4s | > 4s |
| FID/INP (Interaction to Next Paint) | < 200ms | 200–500ms | > 500ms |
| CLS (Cumulative Layout Shift) | < 0.1 | 0.1–0.25 | > 0.25 |
| TTFB (Time to First Byte) | < 800ms | 800ms–1.8s | > 1.8s |
Next.js Performance Patterns
Image Optimization
import Image from 'next/image'
// ✅ Correct
<Image
src="/hero.jpg"
alt="Hero image"
width={1200}
height={630}
priority // for LCP images
sizes="(max-width: 768px) 100vw, 50vw"
quality={85}
/>
// ❌ Wrong
<img src="/hero.jpg" alt="Hero" />
Dynamic Import / Code Splitting
import dynamic from 'next/dynamic'
// ✅ Lazy load large components
const HeavyChart = dynamic(() => import('./HeavyChart'), {
loading: () => <ChartSkeleton />,
ssr: false, // for client-only components
})
// ✅ Modals, drawers — load only when opened
const Modal = dynamic(() => import('./Modal'))
Font Optimization
import { Inter, Roboto_Mono } from 'next/font/google'
const inter = Inter({
subsets: ['latin'],
display: 'swap', // prevents CLS
preload: true,
variable: '--font-inter',
})
React Suspense + Streaming
// ✅ Stream large data lists
import { Suspense } from 'react'
export default function Page() {
return (
<>
<FastComponent /> {/* renders immediately */}
<Suspense fallback={<ListSkeleton />}>
<SlowDataList /> {/* streamed */}
</Suspense>
</>
)
}
Bundle Analysis
# Next.js bundle analyzer
ANALYZE=true next build
# Check package sizes
npx bundlephobia <package-name>
# Find duplicate dependencies
npx duplicate-package-checker-webpack-plugin
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.
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.
- 1mo ago First seen · 211 lines · 54 tokens per session scan A 7a1163b15ef5
web-performance is a skill published in the GitHub repository mtnyilmaz/agents (6 stars, last pushed 5mo ago), licensed MIT. It adds 54 tokens to every session and 1,271 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-08-31.
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