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21st

21st is a plugin for Claude Code from 21st-dev/claude-code-plugin. Its manifest loads nothing; the 7 skills, 1 MCP server it bundles cost 1,055 tokens per session together, scanned A, original, Apache-2.0.

A project-aware UI toolkit for finding, generating, building, reviewing, and publishing user-interface work with 21st.dev. It includes seven skills and a remote MCP server, a service that lets the agent use external tools.

In plain words
What is it for?
Use it for React and shadcn UI work, including finding components, creating interfaces, reviewing them, and publishing them.
Why use it?
It brings UI discovery and production tasks into one add-on for frontend projects.

Plugin for Claude Code

Written for Claude Code: a Claude Code plugin manifest.

not rated 21repo changed 1mo ago A scan tokens not measured original Apache-2.0

Good fit Use it for React and shadcn UI work, including finding components, creating interfaces, reviewing them, and publishing them.

Compare 6 plugins from other repositories ↓
Install in Claude Code
/plugin marketplace add 21st-dev/claude-code-plugin
/plugin install 21st
View source ↗ 21st-dev/claude-code-plugin
Install

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.

Clone the repo
git clone --depth 1 https://github.com/21st-dev/claude-code-plugin

Made for: Claude Code.

Wrote 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.

agentmods badge for 21st

README.md
[![agentmods](https://agentmods.dev/badge/plugins/21st-dev/claude-code-plugin/21st/github.svg)](https://agentmods.dev/plugins/21st-dev/claude-code-plugin/21st)
Your own site
<a href="https://agentmods.dev/plugins/21st-dev/claude-code-plugin/21st"><img src="https://agentmods.dev/badge/plugins/21st-dev/claude-code-plugin/21st/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.

agentmods 80×15 button for 21st

Your own site · 80×15
<a href="https://agentmods.dev/plugins/21st-dev/claude-code-plugin/21st"><img src="https://agentmods.dev/badge/plugins/21st-dev/claude-code-plugin/21st.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session not measured What this adds to a session before it is invoked.
When invoked not measured The manifest loads nothing itself; its 7 skills, 1 MCP server cost 1,055 tokens a session between them.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Security

Grade A, and why

21st 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.

plugins/21st/.claude-plugin/plugin.json · 14 lines

What it actually says

{
  "name": "21st",
  "description": "Find, generate, build, explore, review, and publish project-aware UI with seven verified 21st.dev skills plus the remote 21st MCP server.",
  "version": "0.4.1",
  "author": {
    "name": "21st.dev",
    "url": "https://21st.dev"
  },
  "homepage": "https://21st.dev",
  "keywords": ["react", "shadcn", "ui", "components", "mcp", "frontend", "cli"],
  "repository": "https://github.com/21st-dev/claude-code-plugin",
  "license": "Apache-2.0"
}
Contents

What it installs

The manifest is a name and a version. 7 skills, 1 MCP server travel with it, and installing the plugin installs all of them — 1,055 tokens a session between them. Each is measured on its own page, and each can be installed alone.

Changes

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.

  1. 1mo ago Changed 73714cb8eb0c
  2. 2mo ago First seen · 14 lines scan A c0d3e9760baa

Subscribe to this mod's changes

21st is a plugin published in the GitHub repository 21st-dev/claude-code-plugin (21 stars, last pushed 1mo ago), licensed Apache-2.0. Its token cost is not measured: this kind of file is read by the harness, not the model. 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.

Design and UXFrontend
Related

21st compared with plugins from other repositories

21st next to 6 plugins from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
21st21st-dev/claude-code-pluginPlugin211mo agoApache-2.0A—Claude Code
aio-visual-diffaiocean/claude-pluginsPlugin410d agoMITA—Claude Code
motion-design-skillsiart-ai/motion-design-skillsPlugin2014mo agoMITA—Claude Code
ui-input-skillsancoleman/ai-design-componentsPlugin52711mo agoMITA—Claude Code
hyperstackorkait/hyperstackPlugin11mo agononeA—Claude Code
stark-figma-driveangelostark/stark-figma-drive-mcpPlugin07mo agononeA—Claude Code
humanizerblader/humanizerPlugin65k9d agoMITA—Claude Code