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open_app

Launch installed Android applications by specifying their package name to automate app management tasks on connected devices.

Instructions

Launch an Android application by its package name (e.g. com.google.android.youtube). The app must be installed.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
package_nameYesAndroid package name (e.g. com.google.android.youtube)
device_idNoDevice serial number

Implementation Reference

  • The actual implementation of the openApp function that uses ADB monkey to launch an application by package name.
    export async function openApp(packageName: string, deviceId?: string): Promise<string> {
      const resolved = await deviceManager.resolveDeviceId(deviceId);
      validatePackageName(packageName);
    
      // Use monkey to launch the app (works even without knowing the main activity)
      await adbShell([
        'monkey', '-p', packageName,
        '-c', 'android.intent.category.LAUNCHER',
        '1',
      ], resolved);
    
      deviceManager.touchSession(resolved);
      log.info('App opened', { packageName, deviceId: resolved });
      return packageName;
    }
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. While it states the installation prerequisite, it fails to describe error behavior if the app is missing, whether the operation is synchronous, or what occurs when the optional device_id parameter is omitted.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description consists of exactly two sentences with zero redundancy: the first front-loads the action and primary parameter, while the second states the critical prerequisite. Every word earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter tool with full schema coverage but no output schema or annotations, the description covers the essential prerequisite but leaves gaps regarding default device selection behavior (when device_id is omitted) and failure modes, making it adequate but not comprehensive.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, establishing a baseline of 3. The description reinforces the package_name example from the schema but adds no additional semantic context about the device_id parameter's behavior when omitted or valid formats beyond what the schema already provides.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Launch'), target resource ('Android application'), and mechanism ('by its package name'), effectively distinguishing it from sibling tools like close_app or install_apk through the verb choice and prerequisite clause.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides a clear prerequisite ('The app must be installed') indicating when not to use the tool, but lacks explicit guidance on alternatives (e.g., 'use install_apk if not installed') or differentiation from related app-management tools like get_current_app.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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