Developers

Two MCP servers give your AI assistant structured knowledge of Red Hat Design System components and design tokens. Once configured, your assistant can generate correct RHDS markup, suggest token values, and validate your usage.

Both are also available via go install:

go install bennypowers.dev/cem@latest
go install bennypowers.dev/asimonim@latest

Verify both are installed:

cem version
asimonim version

Pick your editor below and follow the steps. You only need to configure one.

Install both plugins:

/plugin marketplace add bennypowers/cem
/plugin install cem
/plugin marketplace add bennypowers/asimonim
/plugin install asimonim

No additional configuration needed. Both plugins discover RHDS manifests and token files from node_modules automatically.

Add both servers to your Cursor MCP config:

{
  "mcpServers": {
    "cem": {
      "command": "cem",
      "args": ["mcp"]
    },
    "asimonim": {
      "command": "asimonim",
      "args": ["mcp"]
    }
  }
}

For component intelligence, install the Custom Elements Language Server extension from the marketplace.

For MCP support, add both servers to your MCP configuration the same way as Cursor (above).

For Neovim 0.11+ with native LSP support, create two files:

~/.config/nvim/lsp/cem.lua:

return {
  cmd = { 'cem', 'lsp' },
  root_markers = { 'custom-elements.json', 'package.json', '.git' },
  filetypes = { 'html', 'twig', 'php', 'typescript', 'javascript' },
}

~/.config/nvim/lsp/asimonim.lua:

return {
  cmd = { 'asimonim', 'lsp' },
  root_markers = { 'package.json', '.git' },
  filetypes = {
    'css', 'html', 'twig', 'php',
    'javascript', 'javascriptreact',
    'typescript', 'typescriptreact',
    'json', 'yaml',
  },
}

1. Open an HTML or CSS file in a project that depends on @rhds/elements
2. Type <rh- and confirm that autocomplete suggestions appear
3. In a CSS file, type --rh- and confirm that token suggestions appear
4. If using MCP, ask your AI assistant to generate an RHDS component or list available tokens

If completions do not appear, make sure your project has @rhds/elements in its dependencies. If your project has its own web components, you can generate a manifest with:

cem generate

• CEM documentation
• Asimonim documentation