app_zoom

This tool on every surface: CLI · MCP · Python · JavaScript · Go · Java · .NET

Pinch two fingers apart or together, about an element or the middle of the screen. It reports that the gesture was delivered and nothing more. Neither platform puts a zoom level in the accessibility hierarchy, so unlike app_check there is no state to read back — confirming a zoom means asking the thing that was zoomed, and a WebView can answer with visualViewport.scale through app_eval. Pinching about the wrong point scales the right amount in the wrong place, so pass a target when one matters. A direction pinches by a default amount; from and to say exactly how far the fingers travel, the way app_swipe takes either a direction or coordinates. Discards the refs from the last app_map, since anything on screen may now be a different size.

Changes the device, the app or the session: readOnlyHint is false.

Arguments

Name	Type	Required	What it is
device	string		Device serial to target, e.g. "emulator-5554". Omit when only one device is running.
direction	string: in, out		"in" (default) to zoom in, "out" to zoom out.
driver	string: uiautomator2, uiautomator, wda		Driver to use: "uiautomator2" (default for Android; fast, installs a server APK on first use), "uiautomator" (Android, installs nothing, slower, cannot type), or "wda" (WebDriverAgent: iOS simulators and iPhones).
from	integer		Half the distance between the fingers at the start, in device pixels. Give with to instead of a direction, for a pinch of a particular size — one sized to an element, or deliberately small.
target	string		A ref or locator to pinch about. Defaults to the middle of the screen.
to	integer		Half the distance between the fingers at the end. Larger than from zooms in, smaller zooms out. Keep the difference above about 100 device pixels: a shorter travel is below the platform's own threshold and is ignored — measured, 50px of travel left the scale unchanged and 100px moved it to 1.42.

Examples

Each is the arguments of a tools/call request; the first is shown whole.

Pinch out, to zoom in

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "app_zoom",
    "arguments": {
      "direction": "in"
    }
  }
}

On an Android 15 emulator the answer's text was:

pinched in about the screen at (540, 1200), fingers 160 to 640px apart — the gesture was delivered, which is all this can confirm: neither platform reports a zoom level in the hierarchy, so ask the thing you zoomed (a WebView knows its own visualViewport.scale)

Before	After

mobium zoom in on an Android 15 emulator