next-ai-draw-io/packages/mcp-server

Next AI Draw.io MCP Server

MCP (Model Context Protocol) server that enables AI agents like Claude Desktop and Cursor to generate and edit draw.io diagrams with real-time browser preview.

Self-contained - includes an embedded HTTP server, no external dependencies required.

Quick Start

{
  "mcpServers": {
    "drawio": {
      "command": "npx",
      "args": ["@next-ai-drawio/mcp-server@latest"]
    }
  }
}

Installation

Claude Desktop

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json on macOS):

{
  "mcpServers": {
    "drawio": {
      "command": "npx",
      "args": ["@next-ai-drawio/mcp-server@latest"]
    }
  }
}

VS Code

Add to your VS Code settings (.vscode/mcp.json in workspace or user settings):

{
  "mcpServers": {
    "drawio": {
      "command": "npx",
      "args": ["@next-ai-drawio/mcp-server@latest"]
    }
  }
}

Cursor

Add to Cursor MCP config (~/.cursor/mcp.json):

{
  "mcpServers": {
    "drawio": {
      "command": "npx",
      "args": ["@next-ai-drawio/mcp-server@latest"]
    }
  }
}

Cline (VS Code Extension)

1. Click the MCP Servers icon in Cline's top menu bar
2. Select the Configure tab
3. Click Configure MCP Servers to edit cline_mcp_settings.json
4. Add the drawio server:

{
  "mcpServers": {
    "drawio": {
      "command": "npx",
      "args": ["@next-ai-drawio/mcp-server@latest"]
    }
  }
}

Claude Code CLI

claude mcp add drawio -- npx @next-ai-drawio/mcp-server@latest

Other MCP Clients

Use the standard MCP configuration with:

• Command: npx
• Args: ["@next-ai-drawio/mcp-server@latest"]

Usage

1. Restart your MCP client after updating config

2. Ask the AI to create a diagram:

   "Create a flowchart showing user authentication with login, MFA, and session management"

   "Read docs/architecture.md and draw the system as a diagram"

3. The diagram appears in your browser in real-time!

Features

• Real-time Preview: Diagrams appear and update in your browser as the AI creates them
• Drawing Rules: The AI gets the same layout, edge and style rules as the web app, plus the shape library docs (AWS, Azure, GCP, Kubernetes, Cisco and more), so it uses real icon names instead of guessing
• Self-check: The AI can take a screenshot of the rendered diagram (screenshot: true on create_new_diagram or edit_diagram, or screenshot_diagram) and fix overlapping shapes or edges that cross shapes
• Draw from Your Files: ask the AI to draw from a document, image or web page; it reads the source with the host's own tools and draws. Existing .drawio files open with load_diagram
• Edit Support: Modify existing diagrams with natural language instructions. If any change in an edit fails, nothing is written and the AI gets the reason and the current page XML
• Your Edits Are Kept: Changes you make in the browser are read before the AI edits again. If the AI overwrites a change you were still making, your version is saved in History
• Version History: Click History at the top right of the preview page to restore one of the last 20 versions, shown as thumbnails, or ask the AI to undo (restore_version)
• Download and Export: Save as .drawio, .png, .svg, or .drawio.svg (an SVG with the diagram embedded, which draw.io and load_diagram can open again), from the Download button or through export_diagram
• Multi-page: List, add, rename, and delete pages, and edit any page
• Auto-save: Each session's diagram is saved to ~/.next-ai-drawio/<session-id>.drawio, and its last 20 versions to <session-id>.history.json, so the diagram, History and undo survive a restart of the MCP client
• Custom Instructions: keep your own drawing rules in ~/.next-ai-drawio/instructions.md (for example "Always draw in minimal style"); they are appended to the drawing guide on every call
• Themes and Dark Mode: Pick a draw.io theme under Extras > Theme; the page follows the system dark mode, or fix them with DRAWIO_UI, DRAWIO_DARK and DRAWIO_LANG
• Self-contained: Embedded server, works offline (except draw.io UI which loads from embed.diagrams.net by default, configurable via DRAWIO_BASE_URL)

Available Tools

Tool	Description
start_session	Opens browser with real-time diagram preview; the result includes the drawing rules. Pass session_id to continue a saved diagram
list_saved_diagrams	List the auto-saved diagrams of earlier sessions, newest first, with their pages
get_drawing_guide	Return the drawing rules again, for example after a long conversation was compacted, or, with topic, a short XML reference for tables, layers or groups
get_shape_library	Return the shapes and icon styles of a library such as aws4, azure2, or kubernetes
create_new_diagram	Create a new diagram from XML; a plain list of mxCell elements is enough
load_diagram	Load a .drawio or .drawio.svg file into the session, from a path on disk or from its xml content (handles compressed files)
edit_diagram	Edit diagram by ID-based operations (update/add/delete cells); all or nothing
get_diagram	Get the current diagram XML, including your edits in the browser
screenshot_diagram	Return a PNG of a page so the AI can check the rendered diagram
export_diagram	Save diagram to a .drawio, .png, .svg, or .drawio.svg file
list_pages	List every page (tab) with id, name, index, and cell count
add_page	Append a new page without touching existing ones
rename_page	Rename a page
delete_page	Delete a page (refuses to delete the last one)
restore_version	Undo: put an earlier version from History back on the canvas; the current one is kept, so a redo is possible

Continue a Diagram Later

After every change, the diagram is saved as a normal .drawio file in ~/.next-ai-drawio/, named after the session id (for example mcp-mgd0a1b2-x7k2p1.drawio). start_session tells the AI both the id and the file path.

To continue a diagram in a later conversation (for example after claude --resume, or in a new chat), the AI calls start_session with session_id set to that id: the same preview URL opens, the saved diagram is shown, and auto-save keeps writing to the same file. If the id is no longer in the conversation, list_saved_diagrams returns every saved diagram, newest first, with the names and cell counts of its pages, so you can ask for "the architecture diagram from yesterday" and let the AI pick it. load_diagram with the file path still works too, and you can open the file in draw.io yourself.

History comes back with the diagram: the last 20 versions are saved next to it in <session-id>.history.json (without thumbnails). When the AI continues the session with start_session and its session_id, or a preview tab is still open after a restart, the History button shows them again and restore_version can undo to them.

The newest 50 files are kept, each with its History file. Set DRAWIO_DATA_DIR to use another folder, or to off to turn auto-save off.

Custom Instructions

To give the AI your own drawing rules, write them in ~/.next-ai-drawio/instructions.md as Markdown, for example "Always draw in minimal style" or "Label every edge". The file is appended to the drawing guide under a ## Custom Instructions heading each time the guide is returned (start_session, get_drawing_guide and the diagram-workflow prompt), so edits apply without restarting your MCP client. Only the first 5000 characters are used.

DRAWIO_DATA_DIR changes the folder the file is read from; with DRAWIO_DATA_DIR=off the default folder is still used, since the file is only read. The text reaches the model as it is, so keep it to drawing rules you trust.

How It Works

┌─────────────────┐     stdio      ┌─────────────────┐
│  Claude Desktop │ <───────────> │   MCP Server    │
│    (AI Agent)   │               │  (this package) │
└─────────────────┘               └────────┬────────┘
                                          │
                                 ┌────────▼────────┐
                                 │ Embedded HTTP   │
                                 │ Server (:6002)  │
                                 └────────┬────────┘
                                          │
                                 ┌────────▼────────┐
                                 │  User's Browser │
                                 │ (draw.io embed) │
                                 └─────────────────┘

1. MCP Server receives tool calls from Claude via stdio
2. Embedded HTTP Server serves the draw.io UI and handles state
3. Browser shows real-time diagram updates via polling

Configuration

Variable	Default	Description
PORT	6002	Port for the embedded HTTP server
DRAWIO_BASE_URL	https://embed.diagrams.net	Base URL for the draw.io embed. Set this to use a self-hosted draw.io instance for private deployments.
DRAWIO_DATA_DIR	~/.next-ai-drawio	Folder for the auto-saved .drawio files and your instructions.md. Set to off to turn auto-save off (instructions.md is then read from the default folder).
DRAWIO_LANG	unset	Language of the draw.io editor. Unset, draw.io chooses: the browser language on embed.diagrams.net, English on a self-hosted draw.io until the user picks one under Extras > Language. A code such as en, zh, zh-tw, ja or de fixes it and hides that submenu.
DRAWIO_UI	unset	draw.io theme. Unset, the user picks one under Extras > Theme and draw.io remembers it. kennedy, atlas, dark, min, sketch or simple fixes the theme and hides that menu.
DRAWIO_DARK	auto	Dark mode of the draw.io editor: auto follows the system, 1 forces dark, 0 forces light. The page header keeps following the system.
DRAWIO_AUTO_SCREENSHOT	unset	Set to true to attach a screenshot to every create_new_diagram and edit_diagram result, so the AI checks each drawing. Costs 2 to 10 s per call; the preview tab must be open and in front. A call can still pass screenshot: false.
DEBUG	unset	Set to true to log debug messages to stderr.

Private Deployment (Self-hosted draw.io)

For security-sensitive environments that require private deployment of draw.io:

{
  "mcpServers": {
    "drawio": {
      "command": "npx",
      "args": ["@next-ai-drawio/mcp-server@latest"],
      "env": { 
        "DRAWIO_BASE_URL": "https://drawio.your-company.com"
      }
    }
  }
}

You can deploy your own draw.io instance using the official Docker image:

docker run -d -p 8080:8080 jgraph/drawio

Then set DRAWIO_BASE_URL=http://localhost:8080 (or your server's URL). The preview page loads nothing else from the internet, so with a local draw.io it works offline. One exception: shapes from the Material Design library show icons from fonts.gstatic.com.

Without DRAWIO_BASE_URL the preview uses the trimmed draw.io copy bundled with this package. It has the editor, the shape libraries, the templates and PlantUML; features that load more code when used (Mermaid, for example) are not included. Set DRAWIO_BASE_URL to a full draw.io if you need them.

Troubleshooting

Port already in use

If port 6002 is in use, the server will automatically try the next available port (up to 6020).

Or set a custom port:

{
  "mcpServers": {
    "drawio": {
      "command": "npx",
      "args": ["@next-ai-drawio/mcp-server@latest"],
      "env": { "PORT": "6003" }
    }
  }
}

"No active session"

Call start_session first to open the browser window.

Browser not updating

Check that the browser URL has the ?mcp= query parameter. The MCP session ID connects the browser to the server.

Screenshot or PNG/SVG export times out

PNG and SVG files are rendered by draw.io in the preview tab. Browsers slow down tabs that stay in the background, so the tab may not answer in time. Bring the preview tab to the front and try again.

Preview is blank inside VS Code Simple Browser

The preview page refuses to be embedded in other pages (it sends Content-Security-Policy: frame-ancestors 'self'), so in-editor browsers such as VS Code Simple Browser, Cursor's built-in browser or a port forward's "Preview in Editor" show a blank page. Open the Browser URL from the start_session result in a regular browser (Chrome, Edge, Firefox, Safari) instead.

License

Apache-2.0