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Allows AI agents to create and modify interactive software architecture diagrams on the Composer canvas. Provides tools for managing diagrams, adding nodes (services, databases, queues, caches, etc.) and connections, defining APIs, verifying diagram integrity, and linking diagram elements to source code files in real-time.

composer-mcp by OliverGrabner

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

Getting Started

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

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

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

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

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

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

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

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

Add to .continue/config.yaml:

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

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

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

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

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

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security - not tested

A

license - permissive license

-

quality - not tested

How are these scores calculated?

Resources

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