Show HN: UML Modeling Powered by AI Agents – Astah Pro MCP

A local MCP server that runs as a plugin for Astah Professional, a UML modeling tool. This MCP server enables you to do the following and more:

• Use AI to design systems and represent them as UML models and diagrams in Astah.
• Ask AI to explain UML models and diagrams in your Astah project.
• Generate source code from UML models and diagrams in your Astah project, and vice versa.
• Create UML diagrams in Astah from hand-drawn sketch images.

The videos below show Claude Code designing a simple library management system and drawing a class diagram, a sequence diagram, and an activity diagram. These videos are sped up 5×.

Prompt: Design a simple library management system and draw a class diagram in Astah to represent its structure.

Prompt: Draw a sequence diagram to illustrate the behavior of borrowing a book.

Prompt: Draw an activity diagram to illustrate the behavior of returning a book.

Note: As of October 10, 2025, AI assistants/agents are reasonably good at viewing and editing model information, but their ability to view and edit visual diagram information is still developing.

• Astah Professional v10.1 or later is required. This does not work with Astah UML.

• Supported AI assistants/agents

  • Claude Desktop
  • Claude Code
  • Codex CLI
  • Gemini CLI
  
  

  Note 1: This MCP server exposes 200+ tool functions. Other AI assistants/agents may fail to connect due to the large number of tools, or may connect but only recognize a subset.

  Note 2: This MCP server only connects to AI assistants/agents running on the same machine as Astah Professional. Under Astah's terms of use, using Astah via an AI assistant/agent running on a different machine is not permitted. For questions about these terms, please contact Change Vision (the developer of Astah) directly.

  Tip: This is just the personal impression, but we recommend Claude Code or Claude Desktop because they use tool functions more appropriately. Additionally, if processing speed is your priority, go with Claude Code.

This MCP server can view and edit the following diagrams (with more to come):

• Class Diagram
• Sequence Diagram
• Activity Diagram

Download from here and install.

Download the plugin JAR file (astah-pro-mcp-x.x.x.jar), drop it into Astah, then restart Astah (see here). After restarting, if you see an 'mcp' tab in Astah's extensions view, the installation was successful.

Add the following settings to connect to the MCP server using the Streamable HTTP transport.

claude_desktop_config.json

As of October 10, 2025, Streamable HTTP connections to a local MCP server don't seem to work well in Claude Desktop. Use a bridge such as mcp-remote, which requires Node.js v20 or later.

.mcp.json

Or run this command:

See here for information on the --scope flag.

config.toml

As of October 10, 2025, Streamable HTTP connections to a local MCP server don't seem to work well in Codex CLI. Use a bridge such as mcp-remote, which requires Node.js v20 or later.

settings.json

Note: Use 127.0.0.1 instead of localhost. Connections to localhost will fail.

1. Start Astah (starting Astah also starts the MCP server).
   Some AI assistants/agents try to connect to the MCP server on startup, so start Astah first.

2. Start the AI assistant/agent.
   On the first connection to the MCP server, you will be asked to confirm. Review the details and click 'Connect'.
   

3. Send prompts to the AI assistant/agent.

Troubleshooting: If Claude Desktop cannot connect to the MCP server, completely quit Claude Desktop (e.g., end the 'Claude' process in Task Manager), then restart it.

If you want to build and test locally:

1. Set up your Astah plugin development environment (see here).

2. Build:

3. Run tests (update astahPath to match your Astah Professional installation path):

   Run all tests on Windows 11:

   astah-mvn test -DastahPath="C:\Program Files\astah-professional"

   Run specific tests on Windows 11:

   astah-mvn test -DastahPath="C:\Program Files\astah-professional" -Dtest="**/editor/*Test"

This project is currently experimental. The design and implementation may undergo breaking changes.

Astah project data and logs will be shared with the AI assistant/agent. For Astah projects that contain confidential information, either refrain from using this MCP server or use it only with appropriate safeguards (e.g., enabling opt-out settings for AI assistants/agents).

Because this MCP server edits models and diagrams, we recommend committing your Astah project to a Git repository or making copies before and during use so you can revert if necessary.

Some model or diagram information (e.g., certain properties) cannot be viewed or edited via the provided tool functions. Use the Astah GUI directly for those.

This MCP server prioritizes providing the information AI assistants/agents need and does not implement token-saving measures. We recommend using AI assistants/agents on a flat-rate plan rather than pay-as-you-go.

As with source code, AI assistants/agents can make mistakes or misinterpret UML models and diagrams.

Some tool functions provided by this MCP server return excerpts from the OMG UML 2.5.1 and OMG SysML 1.7 specifications. These specifications are licensed as stated at the beginning of each document. When a tool function returns such material, it explicitly indicates that it is an excerpt.

All other source code is copyrighted by Takaaki Teshima and released under the MIT-0 license.

Please open an issue. Because this project is experimental phase and may introduce breaking changes, we aren't accepting pull requests until the design and implementation stabilize. Thank you for your understanding.

If you need private support, contact takaaki.teshima.dev [at] gmail.com (replace [at] with @). It could become a paid project; I may still be able to support you/it.