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canvas - Claude MCP Skill
Canvas Skill
SEO Guide: Enhance your AI agent with the canvas tool. This Model Context Protocol (MCP) server allows Claude Desktop and other LLMs to canvas skill... Download and configure this skill to unlock new capabilities for your AI workflow.
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SKILL.md# Canvas Skill
Display HTML content on connected OpenClaw nodes (Mac app, iOS, Android).
## Overview
The canvas tool lets you present web content on any connected node's canvas view. Great for:
- Displaying games, visualizations, dashboards
- Showing generated HTML content
- Interactive demos
## How It Works
### Architecture
```
┌─────────────────┐ ┌──────────────────┐ ┌─────────────┐
│ Canvas Host │────▶│ Node Bridge │────▶│ Node App │
│ (HTTP Server) │ │ (TCP Server) │ │ (Mac/iOS/ │
│ Port 18793 │ │ Port 18790 │ │ Android) │
└─────────────────┘ └──────────────────┘ └─────────────┘
```
1. **Canvas Host Server**: Serves static HTML/CSS/JS files from `canvasHost.root` directory
2. **Node Bridge**: Communicates canvas URLs to connected nodes
3. **Node Apps**: Render the content in a WebView
### Tailscale Integration
The canvas host server binds based on `gateway.bind` setting:
| Bind Mode | Server Binds To | Canvas URL Uses |
| ---------- | ------------------- | -------------------------- |
| `loopback` | 127.0.0.1 | localhost (local only) |
| `lan` | LAN interface | LAN IP address |
| `tailnet` | Tailscale interface | Tailscale hostname |
| `auto` | Best available | Tailscale > LAN > loopback |
**Key insight:** The `canvasHostHostForBridge` is derived from `bridgeHost`. When bound to Tailscale, nodes receive URLs like:
```
http://<tailscale-hostname>:18793/__openclaw__/canvas/<file>.html
```
This is why localhost URLs don't work - the node receives the Tailscale hostname from the bridge!
## Actions
| Action | Description |
| ---------- | ------------------------------------ |
| `present` | Show canvas with optional target URL |
| `hide` | Hide the canvas |
| `navigate` | Navigate to a new URL |
| `eval` | Execute JavaScript in the canvas |
| `snapshot` | Capture screenshot of canvas |
## Configuration
In `~/.openclaw/openclaw.json`:
```json
{
"canvasHost": {
"enabled": true,
"port": 18793,
"root": "/Users/you/clawd/canvas",
"liveReload": true
},
"gateway": {
"bind": "auto"
}
}
```
### Live Reload
When `liveReload: true` (default), the canvas host:
- Watches the root directory for changes (via chokidar)
- Injects a WebSocket client into HTML files
- Automatically reloads connected canvases when files change
Great for development!
## Workflow
### 1. Create HTML content
Place files in the canvas root directory (default `~/clawd/canvas/`):
```bash
cat > ~/clawd/canvas/my-game.html << 'HTML'
<!DOCTYPE html>
<html>
<head><title>My Game</title></head>
<body>
<h1>Hello Canvas!</h1>
</body>
</html>
HTML
```
### 2. Find your canvas host URL
Check how your gateway is bound:
```bash
cat ~/.openclaw/openclaw.json | jq '.gateway.bind'
```
Then construct the URL:
- **loopback**: `http://127.0.0.1:18793/__openclaw__/canvas/<file>.html`
- **lan/tailnet/auto**: `http://<hostname>:18793/__openclaw__/canvas/<file>.html`
Find your Tailscale hostname:
```bash
tailscale status --json | jq -r '.Self.DNSName' | sed 's/\.$//'
```
### 3. Find connected nodes
```bash
openclaw nodes list
```
Look for Mac/iOS/Android nodes with canvas capability.
### 4. Present content
```
canvas action:present node:<node-id> target:<full-url>
```
**Example:**
```
canvas action:present node:mac-63599bc4-b54d-4392-9048-b97abd58343a target:http://peters-mac-studio-1.sheep-coho.ts.net:18793/__openclaw__/canvas/snake.html
```
### 5. Navigate, snapshot, or hide
```
canvas action:navigate node:<node-id> url:<new-url>
canvas action:snapshot node:<node-id>
canvas action:hide node:<node-id>
```
## Debugging
### White screen / content not loading
**Cause:** URL mismatch between server bind and node expectation.
**Debug steps:**
1. Check server bind: `cat ~/.openclaw/openclaw.json | jq '.gateway.bind'`
2. Check what port canvas is on: `lsof -i :18793`
3. Test URL directly: `curl http://<hostname>:18793/__openclaw__/canvas/<file>.html`
**Solution:** Use the full hostname matching your bind mode, not localhost.
### "node required" error
Always specify `node:<node-id>` parameter.
### "node not connected" error
Node is offline. Use `openclaw nodes list` to find online nodes.
### Content not updating
If live reload isn't working:
1. Check `liveReload: true` in config
2. Ensure file is in the canvas root directory
3. Check for watcher errors in logs
## URL Path Structure
The canvas host serves from `/__openclaw__/canvas/` prefix:
```
http://<host>:18793/__openclaw__/canvas/index.html → ~/clawd/canvas/index.html
http://<host>:18793/__openclaw__/canvas/games/snake.html → ~/clawd/canvas/games/snake.html
```
The `/__openclaw__/canvas/` prefix is defined by `CANVAS_HOST_PATH` constant.
## Tips
- Keep HTML self-contained (inline CSS/JS) for best results
- Use the default index.html as a test page (has bridge diagnostics)
- The canvas persists until you `hide` it or navigate away
- Live reload makes development fast - just save and it updates!
- A2UI JSON push is WIP - use HTML files for nowSignals
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Information
- Repository
- clawdbot/clawdbot
- Author
- clawdbot
- Last Sync
- 3/12/2026
- Repo Updated
- 3/12/2026
- Created
- 1/18/2026
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