diagram-mcp

An MCP server that lets AI agents create diagrams through a single tool call. Outputs SVG, Excalidraw, Draw.io, and Mermaid from one API. Uses ELK.js for automatic graph layout.

Installation

npm install -D diagram-mcp

MCP Configuration

Add to your .cursor/mcp.json:

{
  "mcpServers": {
    "diagram": {
      "command": "npx",
      "args": ["diagram-mcp", "--output-dir", "./diagrams"]
    }
  }
}

Options

| Flag | Default | Description | |------|---------|-------------| | --output-dir, -o | . | Directory for generated diagram files |

Tools

createDiagram (primary)

Create a complete diagram in one call. This is the recommended tool — much faster than creating nodes individually.

title:     "my-diagram"
direction: "LR"           # LR (horizontal) or TD (vertical)
nodes:     [{ label, shape, color }]
edges:     [{ from, to, label, style }]
frames:    [{ label, nodeLabels }]
formats:   ["svg"]        # svg, excalidraw, drawio, mermaid

Omit x/y on nodes to use automatic ELK layout.

Other tools

| Tool | Description | |------|-------------| | createNode | Add a single node | | createEdge | Connect two nodes | | deleteElement | Remove a node or edge | | getDiagramState | Get diagram as markdown | | exportDiagram | Export to a specific format | | setStyle | Update colors / stroke | | createFrame | Group nodes into a frame |

Shapes

| Shape | Use for | |-------|---------| | rectangle | Services, modules, components | | cylinder | Databases, caches, storage | | ellipse | Clients, users, external actors | | diamond | Decision points, guards, routers | | hexagon | Infrastructure (CDN, load balancer) | | parallelogram | Interceptors, middleware |

Colors

light-blue, light-green, light-red, light-yellow, light-purple, light-orange, white, gray

Export Formats

| Format | Extension | Opens in | |--------|-----------|----------| | svg | .svg | Any browser or image viewer | | excalidraw | .excalidraw | Excalidraw web or VS Code extension | | drawio | .drawio | draw.io web or VS Code extension | | mermaid | .mermaid.md | Any markdown previewer |

License

MIT