---
name: stitch-mcp-update-design-system
description: Updates an existing Stitch Design System's theme, tokens, or guidelines. Requires the asset name from create or list operations.
allowed-tools:
  - "stitch*:*"
---

# 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

```json
{
  "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:

```json
{
  "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