Dgmo MCP

What dgmo-mcp does

dgmo-mcp exposes Diagrammo's DGMO markup through MCP tools. Agents can turn concise text definitions into SVG or PNG output and work with diagram types such as sequence diagrams, flowcharts, ER diagrams, C4 architecture diagrams, and Gantt charts. The server also supports chart-type discovery, syntax guidance, examples, validation, browser previews, and multi-section HTML report generation.

The generated markup remains readable and diffable, which makes it suitable for producing diagrams from natural-language requests while retaining a text representation for review or revision. share_diagram creates a URL for the Diagrammo web editor, and open_in_app sends a diagram to the Diagrammo desktop app for editing.

How it works

An MCP client invokes a tool with DGMO markup or a description of the desired visualization. validate_diagram checks syntax and returns parse errors without rendering. render_diagram produces SVG or PNG output, while preview_diagram renders one or more diagrams and opens an HTML preview in a browser. generate_report creates an HTML report with multiple sections, a table of contents, and optional source content.

Rendering happens locally, so diagram data stays on the machine running the server for those operations. Browser and desktop actions also occur on the machine hosting the server. The server can run over standard input/output for a local MCP client or as a streamable HTTP endpoint for clients and agents that connect remotely. HTTP requests are handled independently, without persistent sessions.

Setup and configuration

The package can be run directly with npx:

npx -y @diagrammo/dgmo-mcp

For a local MCP client, configure the command as the server process:

{
  "mcpServers": {
    "dgmo": {
      "command": "npx",
      "args": ["-y", "@diagrammo/dgmo-mcp"]
    }
  }
}

The Diagrammo CLI can also install the MCP configuration automatically with dgmo install, or run the server through dgmo mcp.

To serve MCP over HTTP, use --http or set MCP_TRANSPORT=http:

npx -y @diagrammo/dgmo-mcp --http

The HTTP endpoint defaults to 127.0.0.1:3333/mcp. MCP_PORT, MCP_HOST, MCP_PATH, MCP_ALLOWED_HOSTS, and MCP_ALLOWED_ORIGINS adjust the listener and request checks. The HTTP server has no built-in authentication; expose it beyond a trusted local or container network only behind externally managed authentication.

Cloud-space operations require a Diagrammo space API key in DGMO_API_KEY. The key is read from the server environment rather than passed as a tool argument.

Tools and capabilities

• Render DGMO markup as SVG or PNG.
• Validate markup and return parsing errors without rendering.
• Recommend chart types from a natural-language description.
• List supported chart types and identify beta types.
• Retrieve DGMO syntax reference material and chart-specific examples.
• Create Diagrammo web-editor links or open diagrams in the desktop app.
• Check whether the desktop app is installed.
• Open HTML previews in a browser.
• Generate multi-section HTML reports with a table of contents and optional source.
• Write, read, and list diagrams in a Diagrammo Cloud space.

Limitations and notes

The browser-preview, HTML-report, desktop-app, and local app-check operations are not available when the server is accessed over HTTP, because they launch software on the server host. The three Cloud-space tools send diagram content to Diagrammo Cloud and require DGMO_API_KEY; other local rendering operations do not use that Cloud service. HTTP deployments need their own authentication layer when reachable from a wider network.