Agent-Skills.md

Agent Skills: Excalidraw Diagram Generator

Generate architecture diagrams as .excalidraw files from codebase analysis. Use when the user asks to create architecture diagrams, system diagrams, visualize codebase structure, or generate excalidraw files.

UncategorizedID: ooiyeefei/ccc/excalidraw

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ooiyeefei/ccc
ooiyeefei
17017

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pnpm dlx add-skill https://github.com/ooiyeefei/ccc/tree/HEAD/skills/excalidraw

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skills/excalidraw/SKILL.md

Skill Metadata

Name
excalidraw
Description
Generate architecture diagrams as .excalidraw files from codebase analysis, with optional PNG/SVG export. Use when the user asks to create architecture diagrams, system diagrams, visualize codebase structure, generate excalidraw files, export excalidraw diagrams to PNG or SVG, or convert .excalidraw files to image formats.

Excalidraw Diagram Generator

Generate architecture diagrams as .excalidraw files directly from codebase analysis, with optional export to PNG and SVG.

Quick Start

User just asks:

"Generate an architecture diagram for this project"
"Create an excalidraw diagram of the system"
"Visualize this codebase as an excalidraw file"

Claude Code will:

  1. Analyze the codebase (any language/framework)
  2. Identify components, services, databases, APIs
  3. Map relationships and data flows
  4. Generate valid .excalidraw JSON with dynamic IDs and labels
  5. Optionally export to PNG and/or SVG using Playwright

No prerequisites: Works without existing diagrams, Terraform, or specific file types.

Critical Rules

1. NEVER Use Diamond Shapes

Diamond arrow connections are broken in raw Excalidraw JSON. Use styled rectangles instead:

| Semantic Meaning | Rectangle Style | |------------------|-----------------| | Orchestrator/Hub | Coral (#ffa8a8/#c92a2a) + strokeWidth: 3 | | Decision Point | Orange (#ffd8a8/#e8590c) + dashed stroke |

2. Labels Require TWO Elements

The label property does NOT work in raw JSON. Every labeled shape needs:

// 1. Shape with boundElements reference
{
  "id": "my-box",
  "type": "rectangle",
  "boundElements": [{ "type": "text", "id": "my-box-text" }]
}

// 2. Separate text element with containerId
{
  "id": "my-box-text",
  "type": "text",
  "containerId": "my-box",
  "text": "My Label"
}

3. Elbow Arrows Need Three Properties

For 90-degree corners (not curved):

{
  "type": "arrow",
  "roughness": 0,        // Clean lines
  "roundness": null,     // Sharp corners
  "elbowed": true        // 90-degree mode
}

4. Arrow Edge Calculations

Arrows must start/end at shape edges, not centers:

| Edge | Formula | |------|---------| | Top | (x + width/2, y) | | Bottom | (x + width/2, y + height) | | Left | (x, y + height/2) | | Right | (x + width, y + height/2) |

Detailed arrow routing: See references/arrows.md

Element Types

| Type | Use For | |------|---------| | rectangle | Services, databases, containers, orchestrators | | ellipse | Users, external systems, start/end points | | text | Labels inside shapes, titles, annotations | | arrow | Data flow, connections, dependencies | | line | Grouping boundaries, separators |

Full JSON format: See references/json-format.md

Workflow

Step 1: Analyze Codebase

Discover components by looking for:

| Codebase Type | What to Look For | |---------------|------------------| | Monorepo | packages/*/package.json, workspace configs | | Microservices | docker-compose.yml, k8s manifests | | IaC | Terraform/Pulumi resource definitions | | Backend API | Route definitions, controllers, DB models | | Frontend | Component hierarchy, API calls |

Use tools:

  • Glob → **/package.json, **/Dockerfile, **/*.tf
  • Grep → app.get, @Controller, CREATE TABLE
  • Read → README, config files, entry points

Step 2: Plan Layout

Vertical flow (most common):

Row 1: Users/Entry points (y: 100)
Row 2: Frontend/Gateway (y: 230)
Row 3: Orchestration (y: 380)
Row 4: Services (y: 530)
Row 5: Data layer (y: 680)

Columns: x = 100, 300, 500, 700, 900
Element size: 160-200px x 80-90px

Other patterns: See references/examples.md

Step 3: Generate Elements

For each component:

  1. Create shape with unique id
  2. Add boundElements referencing text
  3. Create text with containerId
  4. Choose color based on type

Color palettes: See references/colors.md

Step 4: Add Connections

For each relationship:

  1. Calculate source edge point
  2. Plan elbow route (avoid overlaps)
  3. Create arrow with points array
  4. Match stroke color to destination type

Arrow patterns: See references/arrows.md

Step 5: Add Grouping (Optional)

For logical groupings:

  • Large transparent rectangle with strokeStyle: "dashed"
  • Standalone text label at top-left

Step 6: Validate and Write

Run validation before writing. Save to docs/ or user-specified path.

Validation checklist: See references/validation.md

Step 7: Export to PNG/SVG (Optional)

After writing the .excalidraw file, ask the user if they want PNG, SVG, or both exports.

Uses Playwright MCP tools and @excalidraw/utils to programmatically render the diagram — no manual upload to excalidraw.com needed.

Requires: Playwright MCP tools (browser_navigate, browser_run_code, browser_close).

Full export procedure: See references/export.md

Quick Arrow Reference

Straight down:

{ "points": [[0, 0], [0, 110]], "x": 590, "y": 290 }

L-shape (left then down):

{ "points": [[0, 0], [-325, 0], [-325, 125]], "x": 525, "y": 420 }

U-turn (callback):

{ "points": [[0, 0], [50, 0], [50, -125], [20, -125]], "x": 710, "y": 440 }

Arrow width/height = bounding box of points:

points [[0,0], [-440,0], [-440,70]] → width=440, height=70

Multiple arrows from same edge - stagger positions:

5 arrows: 20%, 35%, 50%, 65%, 80% across edge width

Default Color Palette

| Component | Background | Stroke | |-----------|------------|--------| | Frontend | #a5d8ff | #1971c2 | | Backend/API | #d0bfff | #7048e8 | | Database | #b2f2bb | #2f9e44 | | Storage | #ffec99 | #f08c00 | | AI/ML | #e599f7 | #9c36b5 | | External APIs | #ffc9c9 | #e03131 | | Orchestration | #ffa8a8 | #c92a2a | | Message Queue | #fff3bf | #fab005 | | Cache | #ffe8cc | #fd7e14 | | Users | #e7f5ff | #1971c2 |

Cloud-specific palettes: See references/colors.md

Quick Validation Checklist

Before writing file:

  • [ ] Every shape with label has boundElements + text element
  • [ ] Text elements have containerId matching shape
  • [ ] Multi-point arrows have elbowed: true, roundness: null
  • [ ] Arrow x,y = source shape edge point
  • [ ] Arrow final point offset reaches target edge
  • [ ] No diamond shapes
  • [ ] No duplicate IDs

Full validation algorithm: See references/validation.md

Common Issues

| Issue | Fix | |-------|-----| | Labels don't appear | Use TWO elements (shape + text), not label property | | Arrows curved | Add elbowed: true, roundness: null, roughness: 0 | | Arrows floating | Calculate x,y from shape edge, not center | | Arrows overlapping | Stagger start positions across edge |

Detailed bug fixes: See references/validation.md

Reference Files

| File | Contents | |------|----------| | references/json-format.md | Element types, required properties, text bindings | | references/arrows.md | Routing algorithm, patterns, bindings, staggering | | references/colors.md | Default, AWS, Azure, GCP, K8s palettes | | references/examples.md | Complete JSON examples, layout patterns | | references/validation.md | Checklists, validation algorithm, bug fixes | | references/export.md | PNG/SVG export procedure via Playwright |

Output

  • Location: docs/architecture/ or user-specified
  • Filename: Descriptive, e.g., system-architecture.excalidraw
  • Exports (optional): system-architecture.svg and/or system-architecture.png in same directory
  • Testing: Open .excalidraw in https://excalidraw.com or VS Code extension; .svg and .png can be viewed directly or embedded in documentation