Composer README
The full upstream README, mirrored here for reference. Install config, tool schemas, adoption signals, and an original overview live on the Composer listing page.
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.
Getting Started
Connect your IDE
Claude Code:
Cursor — create .cursor/mcp.json in your project root:
Your browser will open for authorization on first use.
Claude Code
Cursor
Create .cursor/mcp.json in your project root:
Codex
VS Code (Copilot Chat)
Create .vscode/mcp.json in your project root:
VS Code (Cline)
Open Cline sidebar > Settings (gear icon) > MCP Servers > Add Remote Server:
VS Code (Continue)
Add to .continue/config.yaml:
Windsurf
Add to ~/.codeium/windsurf/mcp_config.json:
Note: Windsurf uses
"serverUrl"instead of"url".
OpenCode
Create opencode.json in your project root:
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_diagramsthenselect_diagram(orcreate_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
Links
- Composer - the visual architecture canvas
- MCP Protocol - Model Context Protocol spec
- Issues - bug reports and feature requests
License
MIT