@usecomposer/mcp

Composer MCP Server

Give your AI coding agent an architecture canvas.
Design, visualize, and evolve software architecture diagrams - right from your IDE.

Composer is a visual system design tool that lets AI coding agents create and modify interactive architecture diagrams through MCP (Model Context Protocol). Your agent gets tools to add services, databases, queues, and connections, and you get a live canvas at usecomposer.com that updates in real-time.

Your IDE  <-->  MCP Server (this package)  <-->  Composer API  <-->  Your Diagram

Try it now - no account needed:

npx @usecomposer/mcp --demo

Starts the server with sample architecture data so you can explore all the tools.

Getting Started

• Sign up at usecomposer.com
• Add the server to your IDE (see below)
• Authorize in your browser when prompted
• Start building diagrams

Connect your IDE

Claude Code:

claude mcp add --transport http composer https://mcp.usecomposer.com

Cursor — create .cursor/mcp.json in your project root:

{
  "mcpServers": {
    "composer": {
      "type": "http",
      "url": "https://mcp.usecomposer.com"
    }
  }
}

Your browser will open for authorization on first use.

Claude Code

claude mcp add --transport http composer https://mcp.usecomposer.com

Claude Desktop

Add to claude_desktop_config.json:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "composer": {
      "type": "http",
      "url": "https://mcp.usecomposer.com"
    }
  }
}

Cursor

Create .cursor/mcp.json in your project root:

{
  "mcpServers": {
    "composer": {
      "type": "http",
      "url": "https://mcp.usecomposer.com"
    }
  }
}

Codex

codex mcp add composer -- npx -y @usecomposer/mcp --stdio

VS Code (Copilot Chat)

Create .vscode/mcp.json in your project root:

{
  "servers": {
    "composer": {
      "type": "http",
      "url": "https://mcp.usecomposer.com"
    }
  }
}

VS Code (Cline)

Open Cline sidebar > Settings (gear icon) > MCP Servers > Add Remote Server:

{
  "mcpServers": {
    "composer": {
      "type": "http",
      "url": "https://mcp.usecomposer.com"
    }
  }
}

VS Code (Continue)

Add to .continue/config.yaml:

mcpServers:
  - name: composer
    url: https://mcp.usecomposer.com

Windsurf

Add to ~/.codeium/windsurf/mcp_config.json:

{
  "mcpServers": {
    "composer": {
      "serverUrl": "https://mcp.usecomposer.com"
    }
  }
}

Note: Windsurf uses "serverUrl" instead of "url".

OpenCode

Create opencode.json in your project root:

{
  "mcp": {
    "composer": {
      "type": "remote",
      "url": "https://mcp.usecomposer.com"
    }
  }
}

Tools

Diagram Management

Tool	Description
list_diagrams	List all your diagrams. Call this first to find which diagram to work on
create_diagram	Create a new diagram and auto-select it for this session
select_diagram	Select which diagram to work on for this session
rename_diagram	Rename the currently selected diagram

Note: Call list_diagrams then select_diagram (or create_diagram) before using other tools.

Read

Tool	Description
get_graph	Get the full architecture diagram - all nodes and edges
get_node	Get details for a single node including connected edges
search_graph	Search nodes and edges by keyword
get_screenshot	Get a PNG thumbnail of the diagram from the last auto-save

Write

Tool	Description
upsert_node	Create or update a node (service, database, queue, etc.)
upsert_edge	Create or update a connection between two nodes
define_api	Define API endpoints on a backend service node
delete_element	Delete a node or edge from the diagram
link_path	Link a node to a file or folder in your codebase

Plan & Verify

Tool	Description
verify_diagram	Check for issues like missing endpoints or orphaned nodes
plan_import	Step-by-step workflow for importing an existing codebase
get_guide	Reference guide for node types, protocols, and best practices

Node Types

client · frontend · backend · database · cache · queue · storage · external

Edge Protocols

REST · gRPC · GraphQL · WebSocket · TCP · UDP · async · event · internal

Example Prompts

Once connected, try asking your AI agent:

Prompt	What it does
"Import this codebase into Composer"	Scans your repo and builds the architecture diagram
"Create a new Composer diagram called Backend Architecture"	Creates and auto-selects a new diagram
"Add a Redis cache between the API and the database in Composer"	Adds a new node and edges to the diagram
"Add analytics monitoring to the Composer diagram"	Adds observability nodes and connections
"Update the APIs I defined in Composer"	Refreshes endpoint definitions on backend nodes
"Verify my Composer diagram"	Checks for missing endpoints, orphaned nodes, etc.
"Link each Composer node to its source code"	Associates diagram nodes with file paths

How It Works

Authentication is handled via OAuth 2.1 — your browser opens for a one-time consent flow, and you're connected. Tool calls are proxied to the Composer API at mcp.usecomposer.com. Your diagram data lives on Composer's servers. The MCP server itself is stateless.

Changes made through MCP are immediately visible on the Composer canvas via real-time WebSocket sync.

Development

git clone https://github.com/olivergrabner/composer-mcp
cd composer-mcp
npm install
npm run dev        # Watch mode (rebuilds on change)
npm run build      # Production build

Links

• Composer - the visual architecture canvas
• MCP Protocol - Model Context Protocol spec
• Issues - bug reports and feature requests

License

MIT