The sigma-ui mcp command starts a Model Context Protocol server. It gives an AI assistant in your editor read access to the SIGMA-UI registry and to every registry configured in your project, so you can ask for things like "add a login form" or "build a settings page with SIGMA-UI components".

The server only reads. It lists, searches, and shows registry items and returns the npx sigma-ui add command for them. The assistant runs that command like any other terminal command, so you see and approve every change.

Quick start

Run mcp init in your project and pick your client:

npx sigma-ui@latest mcp init --client claude

--client takes claude, cursor, vscode, codex, opencode, or gemini. Leave it out to choose from a list. The command adds a sigma-ui server to the client's project config and keeps any servers that are already there. Then restart the client and try:

• Show me all blocks in the SIGMA-UI registry
• Add the button, dialog, and card components to my project
• Build a sign-up page using SIGMA-UI components and blocks

Configuration

Every client starts the same command, npx sigma-ui@latest mcp, from the project root. If you prefer to edit the config by hand, here is what mcp init writes.

Claude Code

.mcp.json:

{
  "mcpServers": {
    "sigma-ui": {
      "command": "npx",
      "args": ["sigma-ui@latest", "mcp"]
    }
  }
}

Restart Claude Code and run /mcp. The sigma-ui server should show as connected.

Cursor

.cursor/mcp.json:

{
  "mcpServers": {
    "sigma-ui": {
      "command": "npx",
      "args": ["sigma-ui@latest", "mcp"]
    }
  }
}

Enable the server in Cursor Settings → MCP. A green dot next to sigma-ui means it is running.

VS Code

.vscode/mcp.json (GitHub Copilot agent mode):

{
  "servers": {
    "sigma-ui": {
      "type": "stdio",
      "command": "npx",
      "args": ["sigma-ui@latest", "mcp"]
    }
  }
}

Open the file and click Start above the server. If your mcp.json has comments, mcp init leaves it unchanged and prints the snippet to paste instead.

Codex

Codex reads MCP servers from your user config, so mcp init --client codex prints this instead of writing it. Add it to ~/.codex/config.toml and restart Codex:

[mcp_servers.sigma-ui]
command = "npx"
args = ["sigma-ui@latest", "mcp"]

OpenCode

opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "sigma-ui": {
      "type": "local",
      "command": ["npx", "sigma-ui@latest", "mcp"],
      "enabled": true
    }
  }
}

Gemini CLI

.gemini/settings.json:

{
  "mcpServers": {
    "sigma-ui": {
      "command": "npx",
      "args": ["sigma-ui@latest", "mcp"]
    }
  }
}

Other clients

Any client that runs stdio MCP servers works. Use npx as the command and sigma-ui@latest mcp as the arguments, and start it from the project root. To use another folder, add --cwd <path>.

Registries

The server always serves the SIGMA-UI registry, in the style system from your sigma-ui.config.json (tailwind without a config). It also serves every registry in the config's registries field:

{
  "registries": {
    "@acme": "https://registry.acme.com/r/{name}.json",
    "@internal": {
      "url": "https://internal.example.com/r/{name}.json",
      "headers": {
        "Authorization": "Bearer ${REGISTRY_TOKEN}"
      }
    }
  }
}

${NAME} placeholders come from the environment. The server also reads .env and .env.local in the project, so a token in .env.local works without exporting it. Variables already set in the environment win.

Tools

Tool	What it does
get_project_registries	Lists the SIGMA-UI registry and the registries from sigma-ui.config.json, plus the project's style system.
list_items_in_registries	Lists items, optionally by registry and type (ui, block, example), with limit and offset paging.
search_items_in_registries	Searches item names, titles, descriptions, and categories. Every word of the query has to match.
view_items_in_registries	Returns full items: file contents, npm dependencies, and registry dependencies.
get_item_examples_from_registries	Finds usage examples, such as button-demo or date-picker-with-range, and returns their source.
get_add_command_for_items	Returns the npx sigma-ui add command for the items, quoted for the shell.
get_audit_checklist	Returns a checklist for reviewing the added code: imports, styles, dark mode, form autocomplete, accessibility, typecheck.

Examples are registry items too. Each component's main example is named <component>-demo, and the others are named after their file in kebab case (ButtonWithIcon.vue is button-with-icon). npx sigma-ui add button-demo installs one into src/components/example.

Example prompts

Browse and search:

• What components and blocks does SIGMA-UI have?
• Find a date picker with a range in the SIGMA-UI registry
• Show me how the data table example handles column pinning

Build:

• Add a login page with email and password using the login-simple block
• Create a settings form with a name field, an email field, and a notifications switch
• Use components from the @acme registry to build a pricing section

Review:

• Run the SIGMA-UI audit checklist on the components you just added

Troubleshooting

• The server does not start. Run npx sigma-ui@latest mcp in the project. It should wait for input without printing anything. Press Ctrl+C to stop it. If npx cached an old version, run npx clear-npx-cache.
• No tools show up. Restart the client after changing its config, and check that the server is enabled. Cursor shows logs under View → Output → MCP.
• A registry is skipped. List and search report registries they could not read under skipped, with the error. Check the URL and that the variables in its headers are set.
• The wrong style system. The server reads styleSystem from sigma-ui.config.json in the folder it starts in. Pass --cwd if the client starts it somewhere else.