Generate light and dark asset catalogs without a paid design tool

Make colors explicit

Asset generation is a shipped workflow in ios-agent-mcp 2.7.0. It converts a strict JSON token file into a new asset catalog locally. It does not require Figma, an AI model or an API key. Start with semantic names rather than scattering literal colors through SwiftUI views.

{
  "version": 1,
  "colors": {
    "AccentColor": {
      "light": "#2457DB",
      "dark": "#90B4FF",
      "highContrastLight": "#12358F",
      "highContrastDark": "#C7DAFF"
    }
  }
}

Generate a new catalog

npx -y ios-agent-mcp@latest assets --tokens tokens.json --output App/Assets.xcassets

The parent directory must exist. The generator refuses to overwrite an existing catalog. Generate a sibling catalog when reviewing changes, compare the output and merge only the intended assets.

Choose every appearance deliberately

All four color appearances are required; the generator does not invent a dark-mode conversion. Names must be ASCII identifiers and unique ignoring case, with AccentColor present. Values use the documented sRGB hex format. Check contrast against the actual background rather than assuming a high-contrast token name guarantees readability.

Keep icon layers editable

New app scaffolds can retain editable SVG layers and render their composition as an opaque 1024-pixel PNG. Customize placeholder shapes before distributing an app. A flattened PNG is not a native Liquid Glass Icon Composer bundle, and generating it does not certify App Review acceptance.

Inspect in context

Use the named assets in the app, build it and inspect light, dark and higher-contrast appearances. The generator handles catalog structure; you still verify the visual result and accessible usage. Keep these checks in your acceptance criteria so a later design change does not silently undo them.

Full token schema and icon workflow

Decision checkpoints