#Screen Capture

Tools for capturing screenshots, component tree snapshots, querying native UI trees, and performing visual regression testing.

#take_screenshot

Capture the device/simulator screen as a JPEG image (720p).

#Parameters

#Example

// Request
{ "tool": "take_screenshot", "arguments": { "platform": "ios" } }

#Tips

• Returns base64 JPEG and point size metadata for coordinate conversion.
• Prefer assert_text or assert_visible over screenshots when possible — screenshots consume vision tokens.
• iOS only supports simulators, not physical devices.

#take_snapshot

Capture the React Native component tree. Compact text output for massive token savings.

#Parameters

#Example

// Request
{ "tool": "take_snapshot", "arguments": { "maxDepth": 10 } }

// Response (compact text)
- View #app-root uid=RCTView:0
  - View #header
    - Text "Home" uid=header>Text:0
  - TextInput #email-input
  - TouchableOpacity #submit-btn
    - Text "Submit"

// interactive mode: only interactive elements
{ "tool": "take_snapshot", "arguments": { "interactive": true } }

// Response
- TextInput #email-input
- TouchableOpacity #submit-btn

#Tips

• Compact output: Over 90% token savings compared to JSON. Hierarchy is represented by indentation.
• Use interactive: true to show only tappable/input elements, further reducing tokens.
• Use uid values with measureView(uid) via evaluate_script to get exact coordinates.
• Reduce maxDepth for large component trees to limit output size.

#describe_ui

Query the native UI/accessibility tree. Compact text output for significant token savings.

#Parameters

#Example

// Request — iOS point query
{
  "tool": "describe_ui",
  "arguments": { "platform": "ios", "mode": "point", "x": 200, "y": 400 }
}

#Tips

• Compact output: Over 78% token savings compared to JSON/XML. Android shows [clickable], [scrollable], bounds= etc. iOS shows role=, enabled=, frame=.
• Prefer query_selector for querying React Native elements.
• iOS uses idb ui describe-all/describe-point. Android uses uiautomator dump.
• Useful for inspecting native components that aren't part of the React tree (e.g., native alerts, system UI).

#visual_compare

Compare the current screen against a baseline PNG for visual regression testing.

#Parameters

#Example

// Create baseline
{
  "tool": "visual_compare",
  "arguments": {
    "platform": "ios",
    "baseline": "/tmp/baselines/home.png",
    "updateBaseline": true
  }
}

// Compare against baseline
{
  "tool": "visual_compare",
  "arguments": {
    "platform": "ios",
    "baseline": "/tmp/baselines/home.png",
    "saveDiff": "/tmp/diffs/home-diff.png",
    "threshold": 0.05
  }
}

// Response
{
  "pass": false,
  "diffRatio": 0.023,
  "diffPixels": 4821,
  "totalPixels": 209664,
  "threshold": 0.05,
  "message": "Visual difference detected: 2.3% of pixels differ"
}

#Tips

• Use updateBaseline: true to create initial baselines.
• Use selector to compare only a specific component (e.g., #header) instead of the full screen.
• Lower threshold values are stricter (0 = pixel-perfect, 1 = any difference passes).
• Uses sharp + pixelmatch internally.

#Video recording

Start and stop screen recording on the device/simulator. Uses idb on iOS and adb screenrecord on Android. Only one recording can be active per MCP server at a time.

#start_video_recording

Start recording the device screen. The recording continues until you call stop_video_recording.

#Parameters

#Example

{
  "tool": "start_video_recording",
  "arguments": {
    "platform": "ios",
    "filePath": "e2e-artifacts/session.mp4"
  }
}

#Tips

• If a recording is already in progress, the tool returns an error. Call stop_video_recording first.
• On server exit (or session end), any active recording is stopped automatically.

#stop_video_recording

Stop the current recording and save the file to the path given when starting.

#Parameters

#Example

{ "tool": "stop_video_recording", "arguments": { "platform": "ios" } }

#Tips

• Returns the path to the saved file on success.
• iOS: uses idb. Android: uses adb screenrecord (SIGINT to stop and finalize).