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 shennawardana23/skillme --skill core-web-vitalsgit clone --depth 1 https://github.com/shennawardana23/skillmeWrote 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/shennawardana23/skillme/core-web-vitals)<a href="https://agentmods.dev/skills/shennawardana23/skillme/core-web-vitals"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/core-web-vitals/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/shennawardana23/skillme/core-web-vitals"><img src="https://agentmods.dev/badge/skills/shennawardana23/skillme/core-web-vitals.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 | $0.00065 | $0.01258 |
| Opus 5 | $0.00032 | $0.00629 |
| Sonnet 5 | $0.00013 | $0.00252 |
| Haiku 4.5 | $0.00006 | $0.00126 |
Grade A, and why
core-web-vitals 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 11d 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 — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Core Web Vitals optimization
Targeted optimization for the three Core Web Vitals metrics that affect Google Search ranking and user experience.
The three metrics
| Metric | Measures | Good | Needs work | Poor |
|---|---|---|---|---|
| LCP | Loading | ≤ 2.5s | 2.5s – 4s | > 4s |
| INP | Interactivity | ≤ 200ms | 200ms – 500ms | > 500ms |
| CLS | Visual Stability | ≤ 0.1 | 0.1 – 0.25 | > 0.25 |
Google measures at the 75th percentile — 75% of page visits must meet "Good" thresholds.
LCP: Largest Contentful Paint
LCP measures when the largest visible content element renders — usually a hero image, video poster, large background image, <svg> element, or large text block.
In rough order of impact, the common causes are: slow server response (TTFB > 800ms), the LCP image not preloaded with fetchpriority="high", render-blocking CSS/JS in <head>, and client-side-rendered content that isn't present in the initial HTML (fix with SSR/SSG/streaming instead of fetching after mount). Beyond the landed page, the Speculation Rules API can prerender likely-next-page navigations so the LCP a user experiences on the next click is near-instant.
Full code patterns for each fix, the Speculation Rules setup and its caveats, the LCP optimization checklist, and the element-identification script are in references/LCP.md — load it when actually fixing an LCP issue.
INP: Interaction to Next Paint
INP measures responsiveness across ALL interactions (clicks, taps, key presses) during a page visit. It reports the worst interaction (at 98th percentile for high-traffic pages).
Total INP = Input Delay + Processing Time + Presentation Delay
| Phase | Target | Optimization |
|---|---|---|
| Input Delay | < 50ms | Reduce main thread blocking |
| Processing | < 100ms | Optimize event handlers |
| Presentation | < 50ms | Minimize rendering work |
The recurring causes are long synchronous tasks blocking the main thread, event handlers that do heavy work before giving visual feedback, eagerly-loaded third-party scripts, and excessive component re-renders. The fix pattern for the first two is the same: give immediate visual feedback, then yield to the scheduler (scheduler.yield(), falling back to setTimeout(0)) before doing the expensive work.
What ships with it
5 files 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.
- 11d ago First seen · 106 lines · 65 tokens per session scan A bb99ab9f4dbf
core-web-vitals is a skill published in the GitHub repository shennawardana23/skillme (2 stars, last pushed 14d ago), licensed Apache-2.0. It adds 65 tokens to every session and 1,258 once invoked, about $0.0003 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 2026-08-31.
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