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.
npx skills add nimadorostkar/Claude-Skills-collection --skill web-performancegit clone --depth 1 https://github.com/nimadorostkar/Claude-Skills-collectionWrote 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/nimadorostkar/claude-skills-collection/web-performance)<a href="https://agentmods.dev/skills/nimadorostkar/claude-skills-collection/web-performance"><img src="https://agentmods.dev/badge/skills/nimadorostkar/claude-skills-collection/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/nimadorostkar/claude-skills-collection/web-performance"><img src="https://agentmods.dev/badge/skills/nimadorostkar/claude-skills-collection/web-performance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00040 | $0.01201 |
| Opus 5 | $0.00020 | $0.00600 |
| Sonnet 5 | $0.00008 | $0.00240 |
| Haiku 4.5 | $0.00004 | $0.00120 |
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 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.
How it starts
The opening of the file, as written. The whole thing — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Web Performance
Purpose
Make pages fast on the devices people actually use. Performance work without measurement on representative hardware is guesswork, and it is usually spent on the wrong thing.
When to Use
- Core Web Vitals failing in field data.
- A page that feels slow, or a bundle that has quietly grown.
- Before launching anything that matters commercially.
- Diagnosing jank, layout shift, or slow interactions.
Capabilities
- Core Web Vitals: LCP, INP, CLS — diagnosis and remediation.
- Bundle analysis and code splitting.
- Image, font, and asset optimization.
- Caching and CDN header configuration.
- Runtime profiling: long tasks, layout thrashing, memory growth.
Inputs
- Field data (Chrome UX Report, RUM), not just a lab score.
- The bundle, the network waterfall, and a CPU profile.
- The device and network profile of the actual audience.
Outputs
- A ranked list of fixes with expected impact.
- Before/after measurements on throttled hardware.
- Budgets in CI so the improvement holds.
Workflow
- Measure the field, not the lab — Lighthouse on a developer laptop tells you nothing about a mid-range Android on 4G. Start with real-user data and reproduce it with 4x CPU throttling and a Slow 4G profile.
- Find the LCP element — It is nearly always a hero image or a heading blocked by a font or a script. Preload it; do not lazy-load it.
- Fix INP by breaking up long tasks — Interaction latency comes from the main thread being busy. Find tasks over 50ms in the profile and yield, defer, or move them off-thread.
- Fix CLS by reserving space — Every image needs
widthandheightor anaspect-ratio. Every ad slot, embed, and late-loading banner needs a reserved box. - Cut the bundle — Analyze it. One date library, one icon set, or one un-tree-shaken utility library is usually a third of the payload.
- Set the cache headers — Immutable, fingerprinted assets get a one-year
max-age. HTML getsno-cacheand revalidates. - Budget it in CI — Otherwise it regresses within two sprints.
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.
- 9d ago First seen · 105 lines · 40 tokens per session scan A 68733d936abd
web-performance is a skill published in the GitHub repository nimadorostkar/Claude-Skills-collection (26 stars, last pushed 25d ago), licensed MIT. It adds 40 tokens to every session and 1,201 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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