Sketch

Sketch - Collaborative SVG Canvas

Description

Opens a Fabric.js-based SVG editor in the browser for collaborative visual prototyping. Codex can write and read SVG through MCP tools while the user edits interactively. Changes sync in real-time via WebSocket.

Preflight

If the editor shows "disconnected" or WebSocket errors occur, stale server processes may be blocking. Run this before retrying:

pkill -f 'sketch-mcp-server/dist/index.js'

Then reconnect the MCP server (the next tool call will restart it). The server now auto-kills stale instances on startup, but orphaned processes from before this fix may still linger.

Tools Available (via sketch-mcp-server)

• sketch_open_canvas - Open a named canvas (creates if new), launches browser editor
• sketch_get_svg - Read current SVG from a canvas
• sketch_set_svg - Replace entire canvas with new SVG
• sketch_add_element - Add SVG elements without clearing existing content
• sketch_add_textbox - Add a fixed-width text area (Textbox) with word wrapping
• sketch_lock_objects - Lock all current objects (non-selectable, non-movable)
• sketch_unlock_objects - Unlock all objects
• sketch_save_template - Save canvas as reusable JSON template (preserves Textbox widths + lock state)
• sketch_load_template - Load a saved JSON template into a canvas
• sketch_list_templates - List all saved templates
• sketch_set_zoom - Set zoom level (1.0 = 100%), optionally zoom toward a specific point
• sketch_pan_to - Pan the viewport so (x, y) is at the top-left
• sketch_zoom_to_fit - Fit all content in view with padding (call after drawing)
• sketch_capture_screenshot - Capture a PNG screenshot of the canvas (returns image for visual verification)
• sketch_clear_canvas - Clear canvas to blank state (use before streaming)
• sketch_focus_canvas - Bring canvas window to foreground
• sketch_list_canvases - List all active canvases
• sketch_close_canvas - Close a canvas and its browser tab

Usage Patterns

Quick sketch

1. sketch_open_canvas with a name
2. sketch_set_svg or sketch_add_element to draw
3. User edits in browser
4. sketch_get_svg to see changes

Streaming (real-time build-up)

1. sketch_open_canvas with a name
2. sketch_focus_canvas to bring window to front
3. sketch_clear_canvas to start fresh
4. Call sketch_add_element multiple times -- each fragment appears instantly
5. User watches the UI build up in real-time

Multiple canvases

Each canvas opens in its own browser tab. Use different names for different drawings.

Default Visual Style

When generating prototypes, wireframes, diagrams, or schemes, use a minimalist style unless the user specifies otherwise:

• Colors: White/light gray background, black/dark gray for strokes and text. No fills on shapes unless semantically meaningful. Avoid decorative color.
• Strokes: Thin (1-2px), consistent weight. Use slightly heavier weight (2-3px) for emphasis only.
• Typography: Clean, sans-serif. Use size hierarchy for structure (e.g., 24px headings, 16px body, 12px labels). Black or #333 text.
• Shapes: Simple rectangles, lines, circles. Rounded corners (rx=4-8) for UI elements. No drop shadows or gradients.
• Layout: Generous whitespace. Align elements to a grid. Clear visual hierarchy through size and spacing, not color.
• Annotations: Use thin arrows and small labels. Keep secondary to the content.

Only introduce color when it carries meaning (e.g., red for errors, green for success, blue for interactive elements) or when the user explicitly requests a colored/branded style.

SVG tips

• Use standard SVG elements: <rect>, <circle>, <ellipse>, <line>, <path>, <text>, <polygon>, <polyline>
• Include xmlns="http://www.w3.org/2000/svg" on the root <svg> element
• Set width and height on the root SVG (default: 1200x800)
• Colors: use hex colors (#ff0000) -- avoid rgba() as Fabric.js SVG parser may not handle it
• Text: <text x="100" y="100" font-size="24">Hello</text>
• Images: <image href="data:image/png;base64,..." width="200" height="200"/>
• Avoid <defs>, <linearGradient>, <filter> -- Fabric.js has limited support for these