coleam00-excalidraw-diagram-skill

Excalidraw Diagram Skill

A coding agent skill that generates beautiful and practical Excalidraw diagrams from natural language descriptions. Not just boxes-and-arrows - diagrams that argue visually.

Compatible with any coding agent that supports skills. For agents that read from .claude/skills/ (like Claude Code and OpenCode), just drop it in and go.

What Makes This Different

• Diagrams that argue, not display. Every shape/group of shapes mirrors the concept it represents — fan-outs for one-to-many, timelines for sequences, convergence for aggregation. No uniform card grids.
• Evidence artifacts. As an example, technical diagrams include real code snippets and actual JSON payloads.
• Built-in visual validation. A Playwright-based render pipeline lets the agent see its own output, catch layout issues (overlapping text, misaligned arrows, unbalanced spacing), and fix them in a loop before delivering.
• Brand-customizable. All colors and brand styles live in a single file (references/color-palette.md). Swap it out and every diagram follows your palette.

Installation

Clone or download this repo, then copy it into your project's .claude/skills/ directory:

git clone https://github.com/coleam00/excalidraw-diagram-skill.git
cp -r excalidraw-diagram-skill .claude/skills/excalidraw-diagram

Setup

The skill includes a render pipeline that lets the agent visually validate its diagrams. There are two ways to set it up:

Option A: Ask your coding agent (easiest)

Just tell your agent: "Set up the Excalidraw diagram skill renderer by following the instructions in SKILL.md." It will run the commands for you.

Option B: Manual

cd .claude/skills/excalidraw-diagram/references
uv sync
uv run playwright install chromium

Usage

Ask your coding agent to create a diagram:

"Create an Excalidraw diagram showing how the AG-UI protocol streams events from an AI agent to a frontend UI"

The skill handles the rest — concept mapping, layout, JSON generation, rendering, and visual validation.

Customize Colors

Edit references/color-palette.md to match your brand. Everything else in the skill is universal design methodology.

File Structure

excalidraw-diagram/
  SKILL.md                          # Design methodology + workflow
  references/
    color-palette.md                # Brand colors (edit this to customize)
    element-templates.md            # JSON templates for each element type
    json-schema.md                  # Excalidraw JSON format reference
    render_excalidraw.py            # Render .excalidraw to PNG
    render_template.html            # Browser template for rendering
    pyproject.toml                  # Python dependencies (playwright)