core-web-vitals

Optimize Core Web Vitals (LCP, INP, CLS) for better page experience using field and lab evidence. Use when asked to "improve Core Web Vitals", "fix LCP", "reduce CLS", "optimize INP", "page experience optimization", or "fix layout shifts".

Quality

73%

Does it follow best practices?

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tessl review fix ./skills/core-web-vitals/SKILL.md

Quality

Content

67%Weight 40%Scale 1-5

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

A dense, actionable body with a solid measurement workflow and well-structured one-level references. The chief weaknesses are mild over-explanation of known concepts and an inline-heavy LCP section that slightly unbalances the progressive disclosure.

Suggestions

Trim or move explanations of concepts Claude already knows (the metric-definition sentences and the 'usually this is' LCP-element list) to tighten conciseness.

Flesh out the framework quick-fix entries that are currently comment-only (React CLS, Vue CLS) with actual code so every example is executable.

Consider moving the LCP eagerness table and caveats into references/LCP.md to balance the inline detail across the three metrics.

Dimension	Reasoning	Score
Conciseness	The body is mostly efficient with high-value actionable detail, but it explains concepts Claude already knows (metric definitions like 'LCP measures when the largest visible content element renders' and the list of typical LCP elements), which could be trimmed.	3 / 5
Actionability	It provides copy-paste-ready HTML, JS, and framework examples plus an LCP checklist, but the framework quick-fix section includes comment-only entries (e.g. React CLS: 'Always specify dimensions in img tags') with no accompanying code, leaving minor gaps.	4 / 5
Workflow Clarity	The 'Measure before optimizing' section gives a clear 4-step measure-diagnose-fix-re-measure sequence with a re-run verification step and a checklist, but validation is guidance rather than an explicit pass/fail gate, so it stops short of the top anchor.	4 / 5
Progressive Disclosure	References to references/LCP.md, INP.md, and CLS.md are one level deep and well-signaled with 'read when ...' conditions, but the LCP section inlines a large amount of detail (eagerness table, caveats, checklist) that creates a minor organization imbalance versus the delegated INP/CLS sections.	4 / 5
	Total	15 / 20 Passed

Description

78%Weight 40%Scale 1-5

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

A well-constructed description that clearly answers both what and when with concrete, natural trigger phrases and a distinct metric-specific niche. The main weakness is reliance on a single action verb rather than enumerating several distinct capabilities.

Suggestions

Replace or supplement the single verb 'Optimize' with a few distinct concrete actions (e.g., 'diagnose, prioritize, and fix Core Web Vitals regressions') to lift specificity.

Add a couple of broader natural trigger phrases such as 'page speed' or 'make my site faster' to widen trigger-term coverage.

Dimension	Reasoning	Score
Specificity	The description names the domain and concrete targets (LCP, INP, CLS, field and lab evidence) but relies on a single action verb ('Optimize') rather than listing several distinct actions, matching the anchor for domain + 1-2 concrete actions.	3 / 5
Completeness	It explicitly states what the skill does ('Optimize Core Web Vitals (LCP, INP, CLS) ... using field and lab evidence') and provides a concrete 'Use when ...' clause with multiple trigger phrases, clearly answering both what and when.	5 / 5
Trigger Term Quality	It lists natural user phrases with synonyms ('improve Core Web Vitals', 'fix LCP', 'reduce CLS', 'optimize INP', 'fix layout shifts'), giving good keyword coverage, though common variations like 'page speed' or 'make my site faster' are absent.	4 / 5
Distinctiveness Conflict Risk	The metric-specific triggers (fix LCP, reduce CLS, optimize INP) carve a clear niche with minimal conflict risk, but 'page experience optimization' is broad enough to overlap slightly with a general web-performance skill.	4 / 5
	Total	16 / 20 Passed

Validation

93%

Warnings & errors only

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 15 / 16 Passed

Validation for skill structure

Criteria	Description	Result
relative_links	Relative link issues: 3 suspicious	Warning

	Total	15 / 16 Passed

Repository: addyosmani/web-quality-skills
Path: skills/core-web-vitals/SKILL.md
Commit: afa8da9

Reviewed: 5 days ago

Table of Contents

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