MCP Service Example

A playground application that an LLM can test and control through the Model Context Protocol using the built-in MCP server (v3/pkg/application, enabled with -tags mcp).

The page contains a counter, a text input wired to a bound Go method, a drag & drop area and a scrollable list — one widget for each MCP tool category. Simulated mouse input is rendered with an animated cursor inside the window, so you can watch the LLM drive the app.

Running

The MCP service is compiled in only with the mcp build tag:

shell

go run -tags mcp .

In a real project the tag is added automatically by setting an environment variable when building:

shell

WAILS_MCP=1 wails3 build   # or: wails3 build -tags mcp
WAILS_MCP=1 wails3 dev

Without the tag the service is a no-op stub and the app behaves normally.

Connecting a client

The server listens on http://127.0.0.1:9099/mcp (streamable HTTP). Configure the port with the WAILS_MCP_PORT environment variable.

For Claude Code:

shell

claude mcp add --transport http mcp-demo http://127.0.0.1:9099/mcp

Then ask things like:

"List the windows of the app and take a DOM snapshot."
"Click the Increment button three times and verify the counter shows 3."
"Type 'Wails' into the name input, click Greet and tell me the result."
"Drag the blue box onto the drop target."
"Call the bound method main.GreetService.Add with 2 and 40."

Available tools

app_info, windows_list, window_control, js_eval, dom_html, dom_query, screenshot_dom, mouse_move, mouse_click, mouse_drag, mouse_scroll, keyboard_type, keyboard_press, call_bound_method, emit_event, wait_for_event.