Tldraw MCP Server

// rebuild after a latest change cd ~/tldraw-mcp && docker compose up -d --build

//to check whether the tool is available or not curl -s -X POST http://127.0.0.1:3102/mcp
-H 'Content-Type: application/json' -H 'Accept: application/json, text/event-stream'
-d '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}'
| tr ',' '\n' | grep drawArrow

This project integrates tldraw with Claude AI using the Model Context Protocol (MCP). It allows Claude to create and manipulate diagrams based on natural language instructions.

Getting Started

Prerequisites

• Node.js 18+ installed

• Claude Desktop installed

• Visual Studio Code (recommended)

Installation and Setup

1. Clone and install dependencies:

   cd tldraw-mcp
   npm install
   cd server
   npm install

2. Build the server code:

   cd server
   npm run build

3. Configure Claude Desktop:

   Create or edit the Claude Desktop configuration file at %AppData%\Claude\claude_desktop_config.json:

   {
     "mcpServers": {
       "tldrawserver": {
         "command": "node",
         "args": ["D:\\tldraw-mcp\\server\\dist\\index.js"]
       }
     }
   }

   Replace the path with the absolute path to the compiled server file.

Starting the Application

The MCP server and the SSE/HTTP bridge (port 3002) run in a single process that Claude Desktop launches for you from claude_desktop_config.json. Do not start a server manually (npm start / npm run start:http) — a second copy would grab port 3002 and the canvas would attach to the wrong process, so nothing would render.

You only start the frontend yourself:

1. Start the Next.js Frontend:

   # In the root directory
   npm run dev

2. Start Claude Desktop and enable the MCP Server:

   • Launch Claude Desktop

   • Open settings (gear icon)

   • Go to the "Advanced" tab

   • Under "MCP Servers", enable "tldrawserver"

   • Click "Apply"

   Claude Desktop now owns the server process. If you ever restart it and an old copy is still holding port 3002, the freshly launched process automatically asks the stale one to step down and takes over — just refresh the browser to reconnect.

Verifying the Setup

1. Open your browser to http://localhost:3000

2. You should see the tldraw canvas

3. In Claude Desktop, try a command like:

   Create a flowchart with two steps: "Start" and "Process Data"

Testing the System

To fully test the integration, try the following Claude commands:

1. Create a simple diagram:

   Create a rectangle labeled "Database" at position (200, 300) with width 150 and height 100

2. Create and connect shapes:

   Create an ellipse labeled "User" at position (100, 100) with width 120 and height 80,
   and a rectangle labeled "API" at position (300, 100) with width 150 and height 80.
   Then connect the "User" shape to the "API" shape.

3. Create a flowchart:

   Create a flowchart with the following steps:
   1. "Start Process"
   2. "Collect Data"
   3. "Analyze Results"
   4. "Generate Report"

4. Add standalone text:

   Add text "CONFIDENTIAL" at position (400, 50) with font size 24

5. Get a snapshot of the current diagram:

   Take a snapshot of the current diagram

Verifying Event Flow

To verify that events are flowing correctly through the system:

1. Open your browser's developer tools (F12 or Ctrl+Shift+I)

2. Go to the Console tab

3. Look for log messages with prefixes:

   • [EventBus] - Events being broadcast internally

   • [HTTP Server] - Messages from the HTTP server

   • [API] - Messages from the Next.js API routes

   • Log messages from TldrawEditor component

When you issue a command in Claude, you should see a sequence of logs showing the operation moving through each part of the system.

Troubleshooting

• HTTP Server not starting: Check if port 3002 is already in use

• Claude not connecting: Verify the path in claude_desktop_config.json

• Diagram not updating: Check browser console for errors in the event stream

• Types of operations not working: Check log messages for errors in parsing or handling specific operations

• Snapshot functionality issues: Check if snapshot-response events are being correctly processed

Common Issues and Solutions

• Port conflicts: If port 3002 is in use, edit httpServer.ts to use a different port, and update the API routes accordingly

• Timing issues: If operations seem to drop, increase logging and check for race conditions

• Type errors: If you encounter "any" type errors, define proper interfaces in eventBus.ts

• Missing dependencies: Run npm install in both the root and server directories

Related MCP server: tldraw-mcp

Architecture Overview

The application consists of:

1. MCP Server: Handles function calls from Claude AI

2. HTTP Server: Provides Server-Sent Events (SSE) endpoints

3. Next.js Frontend: Renders the tldraw canvas and listens for operations

4. EventBus: Facilitates type-safe communication between components

Key Interactions

1. Creating a Shape

When a user asks Claude to create a diagram element, the following sequence occurs:

sequenceDiagram
    participant User
    participant Claude
    participant MCP Server
    participant EventBus
    participant HTTP Server
    participant Frontend

    User->>Claude: "Draw a rectangle labeled 'Database'"
    Claude->>MCP Server: createShape(type: "rectangle", x: 100, y: 150, ...)
    MCP Server->>EventBus: emit("tldraw-operation", {type: "createShape", ...})
    EventBus->>HTTP Server: notify listeners
    HTTP Server->>Frontend: SSE event
    Frontend->>Frontend: Update tldraw canvas

Step-by-Step Process:

1. User Request: User asks Claude to create a diagram element

2. Claude Analysis: Claude processes the request and calls the appropriate MCP function

3. MCP Function Call: The createShape function is executed with parameters

4. Event Broadcasting: The operation is broadcast through the EventBus

5. HTTP Transmission: The HTTP server forwards the event as an SSE message

6. Frontend Rendering: The frontend receives the event and updates the tldraw canvas

2. Getting a Snapshot

When Claude needs the current state of the diagram:

sequenceDiagram
    participant Claude
    participant MCP Server
    participant EventBus
    participant HTTP Server
    participant Frontend

    Claude->>MCP Server: getSnapshot()
    MCP Server->>EventBus: emit("tldraw-operation", {type: "requestSnapshot", requestId: "abc123"})
    EventBus->>HTTP Server: notify listeners
    HTTP Server->>Frontend: SSE event
    Frontend->>Frontend: Get tldraw snapshot
    Frontend->>HTTP Server: POST /api/snapshot
    HTTP Server->>EventBus: emit("snapshot-response", {requestId: "abc123", snapshot: {...}})
    EventBus->>MCP Server: notify listeners
    MCP Server->>Claude: Return snapshot data

Step-by-Step Process:

1. Snapshot Request: Claude calls the getSnapshot function

2. Request ID Generation: The MCP server generates a unique request ID

3. Snapshot Request Broadcasting: The request is broadcast through EventBus

4. Frontend Processing: The frontend receives the request and captures the current canvas state

5. Snapshot Submission: The frontend sends the snapshot back to the server

6. Response Processing: The EventBus routes the snapshot back to the waiting MCP function

7. Return to Claude: The snapshot data is returned to Claude

Why We Use EventBus

The EventBus provides several important benefits, even in a single-client scenario:

1. Decoupled Architecture

EventBus creates a clean separation between different components:

• MCP server can focus on handling Claude's function calls

• HTTP server can focus on client communication

• Components can communicate without direct references to each other

2. Asynchronous Communication

The EventBus enables asynchronous communication patterns:

• MCP functions can trigger operations without waiting for UI updates

• Snapshot requests can be handled asynchronously with promises

3. Centralized Event Management

All communication flows through a single channel:

• Consistent event handling patterns

• Easier debugging (all events can be logged in one place)

• Simplified error handling

4. Extensibility

The EventBus pattern makes the system more extensible:

• New event types can be added without changing the communication architecture

• Additional listeners can be added without modifying existing code

• Future support for multiple clients would be easier to implement

Getting Started

1. Install dependencies for both the frontend and server:

   # Install Next.js frontend dependencies
   npm install
   
   # Install MCP server dependencies
   cd server
   npm install
   cd ..

2. Build the server, then start only the frontend. Claude Desktop launches the server (which also hosts the HTTP/SSE bridge on port 3002) — do not run it manually, or the duplicate process will fight over port 3002 and the canvas will render nothing.

   # Build the MCP server once (rebuild after editing server/src)
   cd server
   npm run build
   cd ..
   
   # Start the Next.js frontend
   npm run dev

3. Configure Claude Desktop to connect to your MCP server:

   # Run the setup script to automatically configure Claude Desktop
   ./setup-claude.bat

   Or manually update your Claude Desktop configuration file (typically located at %AppData%\Claude\claude_desktop_config.json):

   {
     "mcpServers": {
       "tldrawserver": {
         "command": "node",
         "args": ["PATH_TO_COMPILED_JS_FILE"]
       }
     }
   }

   Replace PATH_TO_COMPILED_JS_FILE with the absolute path to the compiled JavaScript file, e.g., D:\\tldraw-mcp\\server\\dist\\index.js.

4. Open http://localhost:3000 in your browser to see the tldraw interface

5. Restart Claude Desktop and tell it: "I'd like to use the tldrawserver MCP server to draw a diagram"

Project Structure

• server/: MCP server implementation

  • src/: TypeScript source files

    • index.ts: Main MCP server with function definitions

    • httpServer.ts: HTTP server for SSE communication

    • eventBus.ts: Event bus implementation with TypeScript interfaces

  • dist/: Compiled JavaScript files (generated)

  • build.bat: Script to compile TypeScript

  • start.bat: Script to build and run the MCP server

  • start-http.bat: Script to build and run the HTTP server

• app/: Next.js frontend

  • components/TldrawEditor.tsx: Frontend component with tldraw integration

  • api/events/route.ts: Next.js API route for SSE events

  • api/snapshot/route.ts: Next.js API route for snapshots

Tldraw Shape Types

Important note about tldraw's shape types:

Tldraw uses a specific shape type system that differs from our simple descriptive names. The mapping is as follows:

• For basic shapes (rectangle, ellipse, triangle, diamond), tldraw uses a "geo" type with a "geo" property specifying the actual shape

• For text, tldraw uses a "text" type

• For arrows/connectors, tldraw uses an "arrow" type

For example, when we specify a "rectangle" in our API, TldrawEditor.tsx maps this to:

editor.createShape({
  type: "geo",
  props: {
    geo: "rectangle",
    // other properties
  },
});

This mapping is handled automatically in the TldrawEditor component.

Available MCP Tools

The following tools are available to Claude via the MCP server:

• createShape: Create basic shapes (rectangle, ellipse, triangle, diamond)

• connectShapes: Connect two shapes with a bound arrow (by their label/text handle)

• drawArrow: Draw a free-form arrow between two points (not bound to shapes)

• addText: Add standalone text elements

• createFlowchartStep: Create a flowchart step (with optional connection to previous step)

• deleteShape: Delete a single shape by its label/text handle

• deleteShapesByLabels: Delete multiple shapes by their label/text handles

• clearCanvas: Delete all shapes on the current page

• getSnapshot: Get a snapshot of the current diagram

• createPage: Create a new page and switch to it (subsequent shapes land there)

• switchPage: Switch the active page by name

• deletePage: Delete a page by name (cannot delete the only/last page)

• listPages: List all pages and which one is active

Technology Stack

• Backend: Node.js, TypeScript, Model Context Protocol SDK

• Frontend: Next.js, React

• Diagramming: tldraw

• Communication: Server-Sent Events (SSE), EventBus

Type Safety

The project implements TypeScript interfaces for all message types to ensure type safety across the application, including:

• Specific payload types for each event

• Type guards for runtime type checking

• Strong typing for all MCP function parameters

Remote Deployment

To run this on a server and connect Claude over a remote MCP URL (https://<your-domain>/mcp) instead of a local stdio process, see DEPLOY.md. It ships the canvas and the MCP/bridge server as two docker compose containers bound to loopback, with your existing nginx terminating TLS and routing /tldraw-mcp to the MCP endpoint.

Server environment variables:

• MCP_TRANSPORT — stdio (default, local Claude Desktop) or http (remote /mcp)

• PORT — HTTP/SSE + MCP port (default 3002)

• BRIDGE_URL (frontend) — where the Next API routes reach the bridge (default http://localhost:3002)