Pencil Designer

Pencil Designer

This skill provides comprehensive guidance for working with Pencil — a vector design tool that integrates directly into development environments. Pencil bridges design and development by operating within IDEs, enabling designers and developers to collaborate using familiar version control workflows.

When to Use This Skill

• Creating or editing designs in .pen files
• Working with Pencil MCP tools (batch_design, batch_get, etc.)
• Building UI layouts, screens, dashboards, or components
• Managing design libraries and design systems
• Generating code from Pencil designs or importing code into designs
• Working with design variables and theming
• Creating reusable components with slots

Critical Rules

1. NEVER use Read, Grep, or cat to read .pen files — contents are encrypted and only accessible via Pencil MCP tools
2. Always start with get_editor_state() to understand the current context before making changes
3. Use get_screenshot periodically to validate design changes visually
4. Limit batch_design to ~25 operations per call to avoid overwhelming the system

Workflow

Starting a Design Task

1. Call get_editor_state() to check the active .pen file and current selection
2. If no file is open, call open_document('new') for a new file or open_document(path) for existing
3. Call get_guidelines(topic) for relevant design rules (topics: code, table, tailwind, landing-page, slides, design-system, mobile-app, web-app)
4. Call get_style_guide_tags then get_style_guide(tags) for design inspiration when not using an existing design system
5. Use snapshot_layout to understand existing layout structure before inserting

Making Design Changes

Use batch_design(operations) with this operation syntax:

# Insert new node
varName=I("parentId", { type: "frame", width: 200, height: 100, fill: "#FF0000" })

# Copy existing node
copy=C("sourceId", "parentId", { fill: "#00FF00" })

# Replace node(s)
R("nodeId1/nodeId2", { fill: "#0000FF" })

# Update node (reference variables from prior operations)
U(varName+"/childId", { text: "Updated text" })

# Delete node
D("nodeId")

# Move node to new parent at index
M("nodeId", "newParentId", 2)

# Generate AI image
G("nodeId", "ai", "A sunset over mountains")

Discovering Content

• Use batch_get(patterns) to search for nodes by pattern
• Use batch_get(nodeIds) to read specific nodes by ID
• Use search_all_unique_properties to audit property values across the tree
• Use snapshot_layout to see computed layout rectangles

Validating Changes

After making changes, call get_screenshot to render a visual preview. Verify:

• Layout looks correct (alignment, spacing)
• Colors and typography match intent
• Components render properly
• No overlapping or misaligned elements

Node Types

Layout Properties

Frames support flexbox-like layout:

Child sizing: use fixed width/height or "fit_content" / "fill_container".

Styling Properties

Fill

• Solid: { fill: "#3B82F6" } or { fill: { type: "solid", color: "#3B82F6" } }
• Gradient: { fill: { type: "linear_gradient", stops: [...], angle: 0 } }
• Image: { fill: { type: "image", url: "..." } }

Stroke

{ "stroke": { "fill": "#000", "thickness": 1, "alignment": "inside" } }

Effects

{ "effect": [{ "type": "shadow", "x": 0, "y": 4, "blur": 8, "color": "#00000020" }] }

Text

Key properties: fontSize, fontFamily, fontWeight, fontStyle, letterSpacing, lineHeight, textAlign ("left"/"center"/"right"/"justify"), textAlignVertical ("top"/"middle"/"bottom"), textGrowth ("auto"/"fixed-width"/"fixed-width-height").

Other

• opacity: 0-1
• cornerRadius: number or per-corner object
• rotation: degrees (counter-clockwise)
• enabled: boolean (visibility)

Components

Creating Components

Set reusable: true on any node to make it a component origin (magenta bounding box).

Creating Instances

Use ref type: { type: "ref", ref: "componentId", descendants: { "childId": { overrides } } }

Slots

Frames marked with slot property become designated drop zones within components. Only empty frames in component origins can be slots.

Variables and Theming

Defining Variables

Variables act as design tokens — define once, reference everywhere with $variable-name syntax.

Types: color, number, string, boolean

Theme Support

Variables can have theme-conditional values for light/dark mode or other theme axes.

Managing Variables

• get_variables — read current tokens and themes
• set_variables — add or update variables
• AI can import variables from CSS (globals.css) or Figma

Design Libraries

Built-in Libraries

• Shadcn UI — Modern component library
• Halo — UI design system
• Lunaris — Design library
• Nitro — Design framework

Custom Libraries

1. Create a .pen file with components
2. Turn it into a library (creates .lib.pen suffix — irreversible)
3. Import into other .pen files via the Libraries panel

Built-in Icon Libraries

Material Symbols (Outlined/Rounded/Sharp), Lucide Icons, Feather, Phosphor

Design-to-Code / Code-to-Design

Design to Code

Select elements, open AI chat (Cmd/Ctrl+K), and request code generation. Supports React, Vue, Next.js, Svelte, Tailwind CSS, CSS Modules, and any framework.

Code to Design

Keep .pen file in the same workspace as code. AI can recreate code components as Pencil designs.

Variable Sync

Synchronize design variables between Pencil and CSS files bidirectionally.

Import/Export

Import

• Figma: Full files via toolbar import or individual layers via copy/paste (images must be imported separately)
• Images: Drag-and-drop, clipboard paste, or toolbar import (PNG, JPEG, SVG)
• Icons: Built-in libraries or custom SVG

Export

• Elements as PNG, JPEG, WEBP, or PDF via properties panel
• Code generation via AI chat

Best Practices

1. Save frequently — no auto-save yet (Cmd/Ctrl+S)
2. Commit .pen files to Git — they are text-based JSON and diff cleanly
3. Use variables instead of hardcoded values for colors, spacing, and fonts
4. Create components for repeated UI elements to maintain consistency
5. Use descriptive names for layers and components (e.g., dashboard-header, user-card)
6. Validate visually with get_screenshot after batch operations
7. Use snapshot_layout before inserting to understand spatial relationships
8. Iterate progressively — start broad, then refine details
9. Use style guides via get_style_guide when not working with an existing design system

Reference Files

For detailed technical specifications:

• references/pen-format-spec.md — Complete .pen format specification with all property types
• references/mcp-tools-guide.md — Detailed MCP tool reference with usage examples