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 S3YED/appie-kit --skill 21st-devgit clone --depth 1 https://github.com/S3YED/appie-kitWrote 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/s3yed/appie-kit/21st-dev)<a href="https://agentmods.dev/skills/s3yed/appie-kit/21st-dev"><img src="https://agentmods.dev/badge/skills/s3yed/appie-kit/21st-dev/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/s3yed/appie-kit/21st-dev"><img src="https://agentmods.dev/badge/skills/s3yed/appie-kit/21st-dev.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 | $0.00118 | $0.02240 |
| Opus 5.5 | $0.00047 | $0.00896 |
| Sonnet 5.5 | $0.00024 | $0.00448 |
| Haiku 4.5 | $0.00012 | $0.00224 |
Grade A, and why
21st-dev 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 — 163 lines — stays where its author put it; the contents beside it link to each section on GitHub.
21st.dev
21st.dev is the "npm for design engineers" — an open-source community registry (MIT) of high-quality React + Tailwind components, blocks, and hooks. It is shadcn-compatible: every component is installed with the standard npx shadcn@latest add CLI, just pointed at a 21st.dev URL.
Prerequisites
- Node 18+ and
npx - A Next.js / Vite / React Router / Astro project
- Tailwind CSS v3 or v4 (Tailwind 4 requires shadcn CLI v4+, March 2026 or newer)
- React 18 or 19
- shadcn initialized once (writes
components.json,src/lib/utils.ts,src/components/ui/button.tsx, and shadcn theme tokens intoglobals.css)
One-time setup (per project)
# Initialize shadcn — creates components.json, ui/, lib/utils.ts, theme tokens
cd <project-root>
npx --yes shadcn@latest init -d --force
-d uses defaults (Next.js template, base-nova preset). --force overwrites any prior config.
Important — the init step rewrites --background, --foreground, --primary, --accent in globals.css to neutral oklch values. If your project already has brand colors mapped to those CSS variables (Weblyfe does — emerald + gold + snow), you must restore the brand mappings immediately after init:
:root {
/* Keep brand vars */
--brand-emerald: #247459;
--brand-gold: #DFB771;
--brand-snow: #F6FEFC;
/* ... */
/* Re-map shadcn slots to brand */
--background: var(--brand-snow);
--foreground: var(--brand-green-goblin);
--primary: var(--brand-emerald);
--accent: var(--brand-gold);
/* keep the rest of shadcn's tokens (card, popover, secondary, border, ring, etc.) */
}
Also restore --font-sans if you use a custom font variable (shadcn replaces it with var(--font-sans)):
@theme inline {
--font-sans: var(--font-rethink), system-ui, sans-serif;
--font-heading: var(--font-rethink), system-ui, sans-serif;
}
Adding a 21st.dev component
Browse https://21st.dev → pick a component → click "Code" / copy the install URL. Then:
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 · 163 lines · 118 tokens per session scan A 2001bb666658
21st-dev is a skill published in the GitHub repository S3YED/appie-kit (12 stars, last pushed 2mo ago), licensed MIT. It adds 118 tokens to every session and 2,240 once invoked, about $0.0005 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 2026-09-03.
Other skills, from other repositories
ui-design
Designs and builds React/Next/Tailwind UI, audits visual and interaction defects, and stress-tests components with worst-case data. Use when asked to "build a landing page", "extract our design system", "add dark mode", "make this responsive", "remove UI slop", "audit this component", "stress-test this component"…
generic-react-design-system
Complete design system reference for React applications. Covers colors, typography, spacing, component patterns, glassmorphism effects, GPU-accelerated animations, and WCAG AA accessibility. Use when implementing UI, choosing colors, applying spacing, creating components, or ensuring brand consistency.
animation-patterns
Framer Motion patterns, page transitions, skeleton loading, scroll-linked animations, and gesture-based interactions for React.
frontend-design
Guidance for distinctive, intentional visual design when building or reshaping UI, HTML/React artifacts, dashboards, charts, and visual reports. Use before implementation to choose a content-specific structure, typography, and visual system that does not read as a templated default.
dev-shadcn
Integration and customization of shadcn/ui (copy-paste React components, Radix + Tailwind). Trigger when the user wants to install shadcn, add components, customize the theme, or when shadcn/ui usage is detected in the project.
shadcn
You are an expert in shadcn/ui — a collection of beautifully designed, accessible, and customizable React components built on Radix UI primitives and Tailwind CSS. Components are added directly to your codebase as source code, not installed as a dependency.