plantuml

This MCP server exposes PlantUML diagram capabilities to Claude via the MCP protocol. It provides three tools: generate_plantuml_diagram, encode_plantuml, and decode_plantuml. The generate_plantuml_diagram tool creates diagrams from PlantUML code and returns embeddable URLs for SVG or PNG formats, with an option to save the diagram to a local file. The encode_plantuml and decode_plantuml tools help convert PlantUML source to a URL-safe encoded string and back again, enabling easy sharing of diagrams via links. You can also configure Claude to point to your preferred PlantUML server using the PLANTUML_SERVER_URL environment variable, and you can restrict or allow local save locations using PLANTUML_ALLOWED_DIRS. The server supports creating sequence, class, and architecture diagrams and can handle advanced PlantUML features like include directives and external libraries. In practice, you can prompt Claude to generate diagrams, obtain embeddable diagram URLs, and optionally save the outputs locally, all while keeping network usage predictable through a configurable PlantUML server URL.

Prerequisites:

• Node.js 18+ and npm installed on your system
• Access to run npx (via npm packages)

Installation steps:

1. Install Node.js and npm from https://nodejs.org/
2. Verify installation:
   • node -v
   • npm -v
3. Run the MCP server using npx (no permanent install required):
   • npx plantuml-mcp-server This will start the PlantUML MCP server using the default PlantUML server at https://www.plantuml.com/plantuml unless overridden.

Optional: Persist the server setup in Claude Desktop configuration 4) If you want Claude Desktop to automatically configure the MCP server, add the following to Claude Desktop MCP config (replace as needed): { "mcpServers": { "plantuml": { "command": "npx", "args": ["plantuml-mcp-server"], "env": { "PLANTUML_SERVER_URL": "https://www.plantuml.com/plantuml" } } } }

Notes:

• You can run with a different PlantUML server by changing PLANTUML_SERVER_URL.
• To run in the background or as a service, consider using your system's process manager with the same command and environment variables.

Tips and common issues:

• Ensure PLANTUML_SERVER_URL points to a valid PlantUML server compatible with the MCP client.
• When saving diagrams locally, by default files are saved only within the current working directory and only .svg and .png are allowed. To permit other directories, set PLANTUML_ALLOWED_DIRS to a colon-separated list of paths or * for any directory.
• If you encounter network or server errors, verify that the PlantUML server URL is reachable and compatible with your PlantUML code.
• Restart Claude (Desktop or Code) after updating the MCP configuration to ensure changes take effect.
• The npm_package field indicates the MCP package exposed via npx (plantuml-mcp-server). If you switch to a non-npx workflow, you can update the mcp_config accordingly.