Plantuml Web

What 2niuhe/plantuml_web MCP server does

The 2niuhe/plantuml_web MCP server adds PlantUML operations to MCP-compatible AI clients. It provides two tools: one converts PlantUML source into a diagram image, and the other checks the source and returns a validation result with detailed error information. Image output can be generated in SVG or PNG format.

The project also includes a NiceGUI-based browser interface. That interface provides an editor with live preview, diagram saving and loading, and resizable panels. The web UI is useful for people who want to edit diagrams interactively, while the MCP endpoint is intended for assistant-driven operations.

How it works

The application is composed of three parts when started using the supplied script: a PlantUML service on port 8000, the web interface on port 8080, and the MCP service on port 8765. MCP clients connect to the SSE endpoint at http://localhost:8765/sse when the services are running locally.

The 2niuhe/plantuml_web MCP server uses the PlantUML 1.2025.3 JAR for diagram processing. An MCP client sends PlantUML code to either the image-generation or syntax-validation tool, depending on whether it needs rendered output or a check of the source.

Setup and configuration

The documented Docker workflow builds an image named plantuml_web_mcp, or runs the published 2niuhe/plantuml_web_mcp:latest image. The container maps port 8080 for the browser interface and port 8765 for MCP access:

docker run -d -p 8080:8080 -p 8765:8765 2niuhe/plantuml_web_mcp:latest

After startup, open http://127.0.0.1:8080 for the web interface and use http://127.0.0.1:8765/sse as the MCP server URL. For a non-Docker setup, install the dependencies from requirements.txt and run start.sh; the script starts all three services and their documented ports.

Claude Desktop can be configured with the SSE URL through its MCP server settings. The repository also includes test_plantuml_mcp.py, which accepts the MCP endpoint URL and can be used to test the running service.

Tools and capabilities

• generate_plantuml_image: renders PlantUML code as an SVG or PNG diagram.
• validate_plantuml_syntax: checks PlantUML code and reports the validation result, including detailed errors.
• NiceGUI web editor: provides live preview, diagram save/load actions, and resizable editor panels.

Limitations and notes

The provided documentation describes an SSE endpoint rather than a local stdio command, so the client must connect to the running HTTP endpoint. The documented local deployment uses fixed ports for the PlantUML service, web interface, and MCP service. The project does not document authentication, environment variables, hosted operation, or additional MCP tools beyond the two listed above.

The 2niuhe/plantuml_web MCP server depends on the included PlantUML version and the services started by Docker or start.sh. If only the MCP functionality is needed, the deployment still starts the related PlantUML and web-interface processes according to the documented startup flow.