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coleam00
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Excalidraw Diagram Skill
by coleam00 · coleam00/excalidraw-diagram-skill
Skill that gives Claude the ability to generate Excalidraw diagrams.
This skill teaches Claude to produce Excalidraw .excalidraw JSON files — architecture diagrams, sequence diagrams, mind maps — that open natively in Excalidraw and stay editable. No screenshot-and-pray.
Why use it
Key features
- Outputs native .excalidraw JSON (fully editable)
- Pre-baked layouts for architecture, sequence, flow, mind map
- Smart auto-layout to avoid label overlap
- Annotation arrows with proper anchoring
- Works in any agent (Claude Code, Cursor, Codex)
Live Demo
What it looks like in practice
excalidraw-diagram-skill.replay
▶ ready
Use Cases
Real-world ways to use Excalidraw Diagram Skill
When to use: You want a diagram you can iterate on, not a static PNG.
Prerequisites
- Server/skill installed and authenticated — See repo README
Flow
-
Describe the system
Using the Excalidraw skill, draw our auth flow: SPA → API gateway → auth-service → Postgres → emit event to Kafka.✓ Copied
→ A .excalidraw file with labeled boxes + arrows
-
Iterate
Add a Redis cache between API gateway and auth-service.✓ Copied
→ Updated file with the new node + correct re-routed arrows
Outcome: A diagram you actually edit, not redraw.
Pitfalls
- For very large diagrams (>30 nodes) auto-layout struggles — For very large diagrams (>30 nodes) auto-layout struggles — split into multiple diagrams or group by concern.
Cost & Limits
What this costs to run
- API quota
- See provider docs for rate limits
- Tokens per call
- Varies by tool
- Monetary
- See repo README for pricing details
- Tip
- Cache tool results and avoid repeated identical calls.
Security
Permissions, secrets, blast radius
Credential storage: Use environment variables; never commit secrets
Data egress: Tool calls go to the provider's API as documented
Troubleshooting
Common errors and fixes
file doesn't open in Excalidraw
Make sure the file ends with .excalidraw and is valid JSON. The skill outputs both, but check the extension.
Verify: Open at excalidraw.com → load file
arrows pointing wrong way
Excalidraw's arrow startBinding/endBinding matters. The skill's templates handle it, but custom edits can break it.
Verify: Reload the file
Alternatives
Excalidraw Diagram Skill vs others
| Alternative | When to use it instead | Tradeoff |
|---|
| BV-Venky/excalidraw-architect-mcp | You want it as an MCP server instead of a skill | MCP is heavier setup; skill is just a folder |