mcp-doc-host

MCP Doc Host — Path B

A Node.js host that bridges MCP (stdio) to a QuikdownEditor running in your browser. The agent drives the editor through Cursor while you watch and interact in a browser tab.

Architecture

Cursor (agent)  ──stdio JSON-RPC──►  start-mcp.js (Node)
                                          │
                           ┌──────────────┼──────────────┐
                           │              │              │
                     filesystem      WebSocket     auto-open
                     sandbox              │
                                          ▼
                                  Browser tab
                                  QuikdownEditor (split mode)
                                  ◄── you interact here

Two surfaces: Cursor for the agent, browser for the human. Both operate on the same document.

Setup

Prerequisites

• Node.js 18+
• quikdown built: npm run build (if running from the repo)
• ws is included in quikdown devDependencies (npm install at repo root)

1. Cursor config

Add to .cursor/mcp.json in your project:

{
  "mcpServers": {
    "quikdown-doc": {
      "command": "node",
      "args": ["examples/mcp-doc-host/start-mcp.js"]
    }
  }
}

2. Start

Restart Cursor. The host starts automatically:

• Opens http://localhost:7744 in your browser
• QuikdownEditor loads in split mode
• Status bar shows "Agent connected" when WebSocket links

3. Use

Ask the agent to edit the document:

"Write a README for a new project called Foobar" "Find all level-2 headings and change them to level-3" "Export the rendered HTML to output.html"

Changes appear live in the browser editor.

Configuration

Env variable	Default	Description
QUIKDOWN_PORT	7744	HTTP + WebSocket port
QUIKDOWN_ROOT	process.cwd()	Filesystem sandbox root

Available tools

All 24 MCP tools are available:

Group	Tools
Headless	markdown_to_html, html_to_markdown, markdown_stats, quikdown_info, markdown_to_ast, markdown_to_json
Filesystem	read_file_info, read_file_lines, read_file_markdown, write_markdown_to_file, write_html_to_file
Editor	read_editor, write_editor, find_regex, replace_regex, replace_text, extract_text, get_stats, get_html, undo, redo, load_file_to_editor, get_rendered, write_rendered_to_file

Headless and filesystem tools run in the Node process. Editor tools are forwarded to the browser over WebSocket.

Known limitations

• Browser must be open before editor tools work. The host starts the server and auto-opens the browser, but if the tab closes, reconnect manually at http://localhost:7744.
• Single client. Only one browser tab connects at a time. Opening a second tab replaces the first connection.
• get_rendered is async. Mermaid/MathJax need time to render in the preview before get_rendered captures them. Allow a brief pause after writing complex fences.
• load_file_to_editor and write_rendered_to_file combine Node filesystem + browser editor. The render step happens in the browser; the file I/O happens in Node.
• No authentication. The WebSocket server binds to localhost only. Do not expose to the network.
• Requires ws package. Install with npm install ws if not already present.

Files

File	Role
start-mcp.js	MCP entry point: stdio listener, HTTP/WS server, browser launcher
editor-host.html	Browser page: QuikdownEditor + WebSocket client
README.md	This file