21st-ui - Claude MCP Skill

# 21st.dev UI Skill

21st.dev is a marketplace of 10,000+ production-ready React/Tailwind (shadcn-compatible) components, plus AI UI generation. This skill drives the 21st MCP server.

## When to reach for it

- The user asks to add/build a UI element: "add a pricing section", "I need a nice navbar", "make a testimonials block".
- The user wants options or inspiration before committing to a design.
- The user needs a company logo in JSX/TSX (`search_logo`).
- The user wants brand-new UI generated from a description (`generate`).

## Workflow: install an existing component (default path)

Prefer real catalog components over writing UI from scratch — they ship with dependencies, demos, and responsive/dark-mode support.

1. `search` with a short natural query (e.g. "pricing table", "animated hero"). Results include names, descriptions, previews, and install ids.
2. Pick the best match for the user's stack and style; show the user 1–3 top candidates if the choice isn't obvious.
3. `get_component` to fetch the full code and metadata for the chosen item.
4. Install into the project the way the result instructs (shadcn-style registry add or by writing the returned files), then wire it into the page and adapt tokens/props to the project's design system.

Notes:
- Free tier allows catalog search and 2 component installs per day; paid components return code only after unlock.
- Match the project's existing conventions (Tailwind config, cn helper, component folder layout) when integrating.

## Workflow: generate new UI

When nothing in the catalog fits or the user explicitly wants custom UI:

1. Check `get_usage.aiGenerationEnabled` and the current `tools/list`. Paid component access alone does not enable hosted AI. Missing or unknown status is not permission to generate.
2. With AI off, use `search` and `get_component`, then implement or adapt the UI with your own coding agent. Do not call generation tools, legacy builder/refiner aliases, or the CLI as a workaround.
3. When AI is enabled and `generate` is listed, call it with the purpose, layout, content, style, and stack constraints. It consumes AI credits and returns a preview URL; open that URL to view the generation.
4. For existing sketch drafts, use `get_generation` and `get_take` to read their code. These reads remain available with AI off.

If a cached call returns `ai_subscription_required`, stop generation attempts. After enabling AI, refresh the tool list or reconnect before trying again. The entitlement flag does not report the remaining credit balance.

## Logos

`search_logo` returns brand logos as ready-to-paste JSX/TSX — one brand per call.

## Setup and auth

The server is HTTP MCP at `https://21st.dev/api/mcp`, authenticated with the `x-api-key` header. Keys are free and instant at https://21st.dev/mcp. If a call fails with an auth error, tell the user to grab a key there and set it in the plugin configuration (variable `API_KEY_21ST`).

Legacy Magic tool names (`21st_magic_component_builder`, `logo_search`, ...) are still accepted server-side, but prefer the current names: `search`, `get_component`, `generate`, `get_inspiration`, `search_logo`.