Stitch MCP — Update Design System

Updates an existing Stitch Design System. Use this to modify theme properties, design tokens, or style guidelines without creating a new design system.

Critical prerequisite

Only use this skill when the user explicitly mentions "Stitch".

You must have the design system's asset name before calling this. If you don't have one:

• List existing design systems via stitch-mcp-list-design-systems
• Or use the name returned from stitch-mcp-create-design-system

When to use

• User wants to modify colors, fonts, or roundness of an existing design system
• After reviewing a design system and wanting to adjust specific properties
• Updating design tokens after a brand refresh

Call the MCP tool

{
  "name": "update_design_system",
  "arguments": {
    "designSystem": {
      "name": "assets/ds_abc123",
      "displayName": "SaaS Dashboard Theme v2",
      "theme": {
        "colorMode": "DARK",
        "font": "GEIST",
        "headlineFont": "GEIST",
        "bodyFont": "GEIST",
        "labelFont": "GEIST",
        "roundness": "ROUND_TWELVE",
        "saturation": 2,
        "customColor": "#818CF8",
        "backgroundLight": "#F9FAFB",
        "backgroundDark": "#09090B"
      },
      "designTokens": "--color-primary: #818CF8;\n--color-bg: #09090B;",
      "styleGuidelines": "Dark mode first. Geist font. Subtle indigo accent."
    }
  }
}

Parameter reference

designSystem — required, Asset wrapper

The object must include the name field (asset identifier) plus any fields you want to update:

Field	Type	Required	Description
name	string	Yes	Asset name from create or list (e.g., assets/ds_abc123)
displayName	string	No	Updated human-readable name
theme	DesignTheme	No	Updated visual configuration (see stitch-mcp-create-design-system for full reference)
designTokens	string	No	Updated CSS custom properties
styleGuidelines	string	No	Updated design rules

Note: This is a full replacement, not a merge. Include all theme fields you want to keep, not just the ones you're changing.

Output

Returns the updated Asset object:

{
  "name": "assets/ds_abc123",
  "displayName": "SaaS Dashboard Theme v2",
  "designSystem": { ... }
}

After updating

• Offer: "Re-apply this updated design system to existing screens?" → stitch-mcp-apply-design-system
• Screens generated before the update won't automatically reflect changes — they need to be re-applied