Web Artifacts Builder
anthropics/skills
Builds multi-component claude.ai HTML artifacts as a small React, TypeScript and Tailwind project, then bundles it into one shareable HTML file.
Analyze frontend performance recordings and propose ranked optimizations.
Install Performance Analysis
$ npx skills add t4t5/rencal --skill performance-analysis -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install t4t5/rencal performance-analysis --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/t4t5/rencal.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/performance-analysis .claude/skills/performance-analysis && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "performance-analysis" agent skill from https://github.com/t4t5/rencal/tree/main/.agents/skills/performance-analysis into .claude/skills/performance-analysis/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "performance-analysis", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/t4t5/rencal/tree/main/.agents/skills/performance-analysisType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add t4t5/rencal --skill performance-analysis -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install t4t5/rencal performance-analysis --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/t4t5/rencal.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/performance-analysis .agents/skills/performance-analysis && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "performance-analysis" agent skill from https://github.com/t4t5/rencal/tree/main/.agents/skills/performance-analysis into .agents/skills/performance-analysis/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "performance-analysis", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add t4t5/rencal --skill performance-analysis -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install t4t5/rencal performance-analysis --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/t4t5/rencal.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/performance-analysis .cursor/skills/performance-analysis && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "performance-analysis" agent skill from https://github.com/t4t5/rencal/tree/main/.agents/skills/performance-analysis into .cursor/skills/performance-analysis/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "performance-analysis", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/t4t5/rencal.git --path .agents/skills/performance-analysis--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add t4t5/rencal --skill performance-analysis -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install t4t5/rencal performance-analysis --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/t4t5/rencal.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/performance-analysis .gemini/skills/performance-analysis && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "performance-analysis" agent skill from https://github.com/t4t5/rencal/tree/main/.agents/skills/performance-analysis into .gemini/skills/performance-analysis/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "performance-analysis", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install t4t5/rencal performance-analysisInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add t4t5/rencal --skill performance-analysis -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/t4t5/rencal.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/performance-analysis .github/skills/performance-analysis && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "performance-analysis" agent skill from https://github.com/t4t5/rencal/tree/main/.agents/skills/performance-analysis into .github/skills/performance-analysis/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "performance-analysis", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add t4t5/rencal --skill performance-analysis -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install t4t5/rencal performance-analysis --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/t4t5/rencal.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/performance-analysis .opencode/skills/performance-analysis && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "performance-analysis" agent skill from https://github.com/t4t5/rencal/tree/main/.agents/skills/performance-analysis into .opencode/skills/performance-analysis/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "performance-analysis", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
performance-analysis- GitHub stars
- 159
- Token cost
- ~461 tokens
- SKILL.md length
- 228 words
- Files
- 1
- Skills in repo
- 6
- Repo updated
- First seen
- Licence
- MIT
At a glance
Analyze frontend performance recordings and propose ranked optimizations.
- Works in 7 steps: Ask for a recording: Ask the user to do… → Analyze the recording: Run just analyze… → Identify bottlenecks: Look at → …
- The user wants to optimize a slow interaction
- Calls just
- Analyze a Chrome/Safari performance trace
What it does
Performance Analysis is an agent skill from t4t5/rencal. Analyze frontend performance recordings and propose ranked optimizations. Use when the user wants to optimize a slow interaction or analyze a Chrome/Safari performance trace.
Its SKILL.md is about 460 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in Frontend & Design. The repository describes itself as: A modern desktop calendar. Built for Omarchy. The licence is MIT.
When your agent uses it
- The user wants to optimize a slow interaction
- Analyze a Chrome/Safari performance trace
Example prompts
- “/performance-analysis”
Workflow steps
7 steps, taken from the first numbered list in SKILL.md.
- Ask for a recording: Ask the user to do a Chrome DevTools performance recording (in Safari Web Inspector or Chrome) of the interaction…
- Analyze the recording: Run just analyze recordings/.json to get a breakdown of rendering frames, layout events, script events, and CPU…
- Identify bottlenecks: Look at
- Read the relevant source code: Based on the CPU profile hotspots, read the source files to understand what the code is doing and why it's…
- Propose optimizations: Present concrete, ranked optimization ideas to the user. Common patterns
- Let the user choose: Don't implement anything until the user picks which optimizations to pursue.
- After implementing: Ask the user to do another recording so you can compare before/after with just analyze and verify the improvements.
What it can do on your machine
Read from SKILL.md and the folder at commit 95f05ce. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
just
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Performance Analysis loads about 461 tokens when it runs. Until then it costs about 49 tokens; SKILL.md has 228 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from t4t5/rencal at commit 95f05ce, republished under its MIT licence (© t4t5). 228 words, ~461 tokens.
Download SKILL.mdSave it as
.claude/skills/performance-analysis/SKILL.md (or your agent's skills folder).- name
- performance-analysis
- description
- Analyze frontend performance recordings and propose ranked optimizations. Use when the user wants to optimize a slow interaction or analyze a Chrome/Safari performance trace.
You are helping the user optimize the performance of a specific part of the app.
Workflow
Ask for a recording: Ask the user to do a Chrome DevTools performance recording (in Safari Web Inspector or Chrome) of the interaction they want to optimize. They should save the recording JSON file in the
recordings/directory.Analyze the recording: Run
just analyze recordings/<filename>.jsonto get a breakdown of rendering frames, layout events, script events, and CPU profile hotspots.Identify bottlenecks: Look at:
- Longest rendering frames — anything over 16ms breaks 60fps
- Top script executions — which events take the most time
- CPU self-time — which functions are burning the most CPU (especially in
src/) - CPU total time — which call trees are the most expensive
Read the relevant source code: Based on the CPU profile hotspots, read the source files to understand what the code is doing and why it's slow.
Propose optimizations: Present concrete, ranked optimization ideas to the user. Common patterns:
- Caching/memoizing repeated computations
- Replacing heavy library calls (e.g. date-fns) with lightweight arithmetic
- Reducing algorithmic complexity (e.g. pre-indexing instead of O(n*m) loops)
- Avoiding unnecessary object allocations (especially Date objects)
Let the user choose: Don't implement anything until the user picks which optimizations to pursue.
After implementing: Ask the user to do another recording so you can compare before/after with
just analyzeand verify the improvements.
© t4t5, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in .agents/skills/performance-analysis of t4t5/rencal.
Open the folder on GitHubat commit 95f05ce
Compare with similar skills
Performance Analysis next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Performance Analysis this skillt4t5/rencal | 159 | — | ~461 | Automated safety check: Pass | MIT | |
| Web Artifacts Builderanthropics/skills | 180k | 40 repos | ~769 | Automated safety check: Pass | Apache-2.0 | |
| React Doctormakeplane/plane | 60k | 12 repos | ~657 | Automated safety check: Pass | AGPL-3.0 | |
| React Composition Patternsvercel-labs/openreview | 1.7k | 58 repos | ~721 | Automated safety check: Pass | MIT | |
| Impeccablebestofjs/bestofjs | 3.1k | 27 repos | ~2.6k | Automated safety check: Pass | MIT | |
| Figma Design System Builderwarpdotdev/warp | 65k | 2 repos | ~4.4k | Automated safety check: Pass | AGPL-3.0 |
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React Composition Patterns
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Rules for structuring React components with composition instead of boolean props, covering compound components, lifted state, variants and React 19 changes.
Impeccable
bestofjs/bestofjs
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Always invoke when the user's message includes 'tailwind' in any form.
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Related
Categories
Questions about Performance Analysis
What does Performance Analysis do?
Analyze frontend performance recordings and propose ranked optimizations. Performance Analysis is an agent skill from t4t5/rencal. Analyze frontend performance recordings and propose ranked optimizations.
When should I use Performance Analysis?
Performance Analysis fits situations like: the user wants to optimize a slow interaction; analyze a Chrome/Safari performance trace.
How do I install Performance Analysis in Claude Code?
Run `npx skills add t4t5/rencal --skill performance-analysis -a claude-code`. Or copy the skill folder (.agents/skills/performance-analysis in t4t5/rencal) into .claude/skills/performance-analysis in your project. Claude Code loads it when a task matches its description.
How do I install Performance Analysis in Codex?
Run `npx skills add t4t5/rencal --skill performance-analysis -a codex`. Or copy the skill folder (.agents/skills/performance-analysis in t4t5/rencal) into .agents/skills/performance-analysis in your project. Codex loads it when a task matches its description.
Can I use Performance Analysis in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add t4t5/rencal --skill performance-analysis -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/performance-analysis, .gemini/skills/performance-analysis, .github/skills/performance-analysis and .opencode/skills/performance-analysis in your project.
What does Performance Analysis need to run?
Going by SKILL.md and its folder, Performance Analysis needs the command-line tools its instructions call (just).
Does Performance Analysis access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Performance Analysis safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Performance Analysis use?
Performance Analysis is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Performance Analysis use?
About 461 tokens (SKILL.md is roughly 1.8k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Performance Analysis?
Skills that share tags, products or a category with Performance Analysis: Web Artifacts Builder (anthropics/skills, 180k stars), React Doctor (makeplane/plane, 60k stars), React Composition Patterns (vercel-labs/openreview, 1.7k stars) and Impeccable (bestofjs/bestofjs, 3.1k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Performance Analysis?
t4t5 (a GitHub user) maintains it in t4t5/rencal, which has 159 GitHub stars. The repository holds 6 skills in this directory. The repository was last updated on October 7, 2026.
Source: t4t5/rencal on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.