staruml-mcp

Model Context Protocol (MCP) server for StarUML. Lets AI agents (Claude Code, Cursor, VS Code Copilot, Codex) drive StarUML programmatically — generate UML diagrams from Mermaid, execute any built-in command, CRUD elements, save projects, and more.

How it fits together

  AI Agent  ──MCP──►  staruml-mcp (this package)  ──HTTP──►  StarUML
                                                  :58321 (built-in, 4 tools)
                                                  :58322 (extension, 15 tools)

Package	What it is	Where it runs
staruml-mcp (this repo)	MCP server for AI agents	your machine via npx -y staruml-mcp
staruml-mcp-extension	StarUML plugin adding 15 HTTP endpoints	inside StarUML (install once via Extension Manager)

• Using only Mermaid-based diagram tools? Install staruml-mcp only. The 4 built-in tools work.
• Want the full 19 tools (project save/open, element CRUD, execute any StarUML command)? Install both.

Prerequisites

• StarUML v7.0.0+ with API Server enabled (see below)
• Node.js 20+ on the machine running the AI agent
• (Optional) staruml-mcp-extension installed in StarUML — required for 15 of the 19 tools

Enable StarUML API Server

Edit settings.json at:

• Windows: %APPDATA%\StarUML\settings.json
• macOS: ~/Library/Application Support/StarUML/settings.json
• Linux: ~/.config/StarUML/settings.json

Add or update:

{
  "apiServer": true,
  "apiServerPort": 58321
}

Restart StarUML.

Verify:

curl http://localhost:58321/
# → "Hello from StarUML API Server!"

Install & Use

Claude Code (recommended — HTTP transport)

Start the server in a terminal:

npx -y staruml-mcp --transport http
# listens on http://localhost:58323/mcp by default

Register with Claude Code:

claude mcp add --transport http staruml http://localhost:58323/mcp

Port 58323 is the canonical HTTP port, chosen to sit alongside StarUML's built-in API (58321) and staruml-mcp-extension (58322). Override with --port <n> if needed.

Restart Claude Code. Ask:

"What StarUML tools do you have?"

Claude Desktop (stdio transport)

Edit %APPDATA%\Claude\claude_desktop_config.json (Windows) or ~/Library/Application Support/Claude/claude_desktop_config.json (macOS):

{
  "mcpServers": {
    "staruml": {
      "command": "npx",
      "args": ["-y", "staruml-mcp"]
    }
  }
}

Restart Claude Desktop.

Cursor / VS Code Copilot / Codex CLI

Point your MCP client at npx -y staruml-mcp (stdio) or http://localhost:58323/mcp (HTTP).

CLI

staruml-mcp [options]

  -t, --transport <type>   stdio | http              (default: stdio)
  -p, --port <number>      HTTP listen port          (default: 58323)
      --api-port <number>  StarUML built-in API port (default: 58321)
      --ext-port <number>  staruml-mcp-extension port(default: 58322)
      --api-host <url>     StarUML API host prefix   (default: http://localhost)
  -V, --version            Print version
  -h, --help               Show help

Tools Exposed

Built-in (always available, port 58321)

Tool	Description
generate_diagram	Generate a UML diagram from Mermaid code.
get_all_diagrams_info	List all diagrams in the current project (id, name, type).
get_current_diagram_info	Get metadata of the currently focused diagram.
get_diagram_image_by_id	Export a diagram as PNG by its ID.

Extension tools (require staruml-mcp-extension, port 58322)

Tool	Description
get_all_commands	List all 138+ built-in StarUML command IDs.
execute_command	Execute any built-in command (e.g. project:save, view:fit-to-window).
get_project_info	Current project's filename + top-level elements.
save_project / save_project_as / new_project / open_project	Project file lifecycle.
get_element_by_id / find_elements	Query model elements.
create_element / update_element / delete_element	Element CRUD.
create_diagram (typed native) / switch_diagram / close_diagram	Diagram management.

To enable extension tools: install staruml-mcp-extension in StarUML (Tools → Extension Manager → Install From URL → https://github.com/ezrabrilliant/staruml-mcp-extension).

Example Prompts

• "Create an ER diagram in StarUML for a POS database: users, menus, transactions with relationships."
• "Generate a sequence diagram for JWT login: frontend → /api/auth/login → AuthService → DB → JWT response."
• "Show me the current diagram in StarUML."
• "Export diagram with ID xyz123 as an image."

Development

git clone https://github.com/ezrabrilliant/staruml-mcp.git
cd staruml-mcp
npm install
npm run dev          # tsx watch on src/
npm run build        # bundle to dist/
npm test             # vitest
npm run typecheck    # tsc --noEmit

Architecture

AI Agent (Claude Code / Cursor / VS Code / …)
        │
        │  MCP (stdio or Streamable HTTP)
        ▼
  staruml-mcp  (this package)
        │
        │  HTTP JSON-RPC
        ▼
StarUML API Server (port 58321)
        │
        ▼
  StarUML Application (v7+)

Acknowledgments

Inspired by staruml/staruml-mcp-server (official stdio-only server by Minkyu Lee, StarUML creator). This project reimplements it with multi-transport support and strict TypeScript.

License

MIT © Ezra Brilliant Konterliem