Returning the image, not just the link, is what makes revision possible.

A model that only gets a URL back has no idea whether the diagram came out right; getting the render as an image means it can spot a broken layout and fix its markup without you describing the problem. Before adopting it, check the official Whimsical server the README points to — this one predates it and is maintained independently.

What it is

A third-party MCP server that creates Whimsical diagrams from Mermaid markup written by the client. It calls Whimsical's API and returns the result in two forms, so the model can review its own diagram and revise it.

What you get

Whimsical diagrams generated from Mermaid markup the client composes
The Whimsical diagram URL, so you can open and keep editing it there
A base64-encoded image alongside it, so the model can see the render and iterate on its own markup

Requirements

Clone the repository, install with yarn and build it, then point your client at the built entry point. Note that Whimsical now publishes an official MCP server of its own, linked from this repository.

Setup effort

Build from source — git clone https://github.com/BrockReece/whimsical-mcp-server.git

See installation options

USE CASES

01

Diagramming a system you just described

Let the assistant write the markup and hand you back a Whimsical board you can keep editing.

02

Getting the layout right without a round trip through you

Let the model look at the returned image and correct its own markup before showing you the result.

03

Moving a diagram into a shared workspace

Take the returned board URL into Whimsical where the rest of the team already works.

INSTALLATION

Connect your client

You clone and build this one yourself.

Server setup

TERMINAL

# Clone the repository
git clone https://github.com/BrockReece/whimsical-mcp-server.git
cd whimsical-mcp-server

# Install dependencies
yarn install

# Build the project
yarn build

MCP Clients

Claude Desktop — local build, Windsurf — local build

JSON

{
  "mcpServers": {
    "whimsical": {
      "command": "node",
      "args": [
        "<YOUR_PATH_TO_THIS>/repo/whimsical-mcp-server/dist/index.js"
      ]
    }
  }
}

Whimsical MCP Server