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      • Element Query

      Tools for finding elements in the React Native component tree and executing JavaScript in the app or WebView context.

      query_selector

      Find the first element matching a selector in the React Fiber tree. Returns UID, type, and measurement (position + size).

      Parameters

      ParameterTypeRequiredDescription
      selectorstringYesSelector for the RN Fiber tree (see Selector Syntax)
      platform"ios" | "android"NoTarget platform
      deviceIdstringNoTarget device

      Example

      // Find by testID
{ "tool": "query_selector", "arguments": { "selector": "#submit-btn" } }

// Find by text content
{ "tool": "query_selector", "arguments": { "selector": ":text(\"Login\")" } }

// Find by hierarchy
{ "tool": "query_selector", "arguments": { "selector": "ScrollView > View > Text" } }

// Response
{
  "uid": "submit-btn",
  "type": "View",
  "testID": "submit-btn",
  "measure": { "pageX": 120, "pageY": 580, "width": 200, "height": 48 }
}

      Tips

      • This is the entry point for most interaction workflows: query_selector → get coordinates → tap.
      • Tap the center of an element: x = pageX + width/2, y = pageY + height/2.
      • UIDs are not known ahead of time — always call query_selector first to discover them.

      query_selector_all

      Find all elements matching a selector. Returns an array with measurements.

      Parameters

      ParameterTypeRequiredDescription
      selectorstringYesSelector for the RN Fiber tree
      platform"ios" | "android"NoTarget platform
      deviceIdstringNoTarget device

      Example

      // Find all list items
{ "tool": "query_selector_all", "arguments": { "selector": "#list-item" } }

// Response
[
  { "uid": "list-item-0", "type": "View", "measure": { "pageX": 0, "pageY": 100, "width": 375, "height": 60 } },
  { "uid": "list-item-1", "type": "View", "measure": { "pageX": 0, "pageY": 160, "width": 375, "height": 60 } }
]

      Tips

      • Prefer query_selector when you only need one element.
      • Use this to enumerate lists, count visible items, or iterate over multiple matches.

      evaluate_script

      Run JavaScript in the app's runtime context. Use measureView(uid) to get tap/swipe coordinates.

      Parameters

      ParameterTypeRequiredDescription
      functionstringYesJS function string. e.g. "() => measureView('my-btn')". require() is not available
      argsarrayNoArguments passed to the function
      platform"ios" | "android"NoTarget platform
      deviceIdstringNoTarget device

      Example

      // Measure a view by UID
{
  "tool": "evaluate_script",
  "arguments": {
    "function": "(uid) => measureView(uid)",
    "args": ["submit-btn"]
  }
}

// Get registered WebView IDs
{
  "tool": "evaluate_script",
  "arguments": {
    "function": "() => getRegisteredWebViewIds()"
  }
}

// Access app globals
{
  "tool": "evaluate_script",
  "arguments": {
    "function": "() => ({ width: globalThis.screen?.width, height: globalThis.screen?.height })"
  }
}

      Tips

      • measureView(uid) returns { pageX, pageY, width, height } — useful for computing tap targets.
      • require() is not available. Only access globals and the built-in MCP helpers.
      • The function is wrapped in a try-catch and executed via WebSocket.

      webview_evaluate_script

      Run JavaScript inside an in-app WebView. Useful for DOM manipulation, form filling, or reading web content.

      Parameters

      ParameterTypeRequiredDescription
      webViewIdstringYesWebView ID. Discover with evaluate_script(() => getRegisteredWebViewIds())
      scriptstringYesJS to run in the WebView (DOM queries, clicks, etc.). Must evaluate to a value for a result
      platform"ios" | "android"NoTarget platform
      deviceIdstringNoTarget device

      Example

      // Get WebView IDs first
{
  "tool": "evaluate_script",
  "arguments": { "function": "() => getRegisteredWebViewIds()" }
}
// Response: ["webview-0"]

// Click a button inside the WebView
{
  "tool": "webview_evaluate_script",
  "arguments": {
    "webViewId": "webview-0",
    "script": "document.querySelector('#login-btn').click(); 'clicked'"
  }
}

      Tips

      • Prefer this over tap for WebView DOM interactions — it's faster and more reliable.
      • WebViews are auto-registered by the babel plugin. Use getRegisteredWebViewIds() to discover available IDs.
      • The script must evaluate to a value to return a result. End with a string or expression.