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Launch an app

android_launch
Idempotent

Launch an installed app's launcher activity on a connected Android device, optionally force-stopping it first for a cold start.

Instructions

Start an installed app's launcher activity, optionally force-stopping it first.

Args:

  • package_name (string, optional): application id, e.g. "com.example.myapp"

  • project_path (string, optional): Gradle root; the package is resolved from it when package_name is omitted

  • module (string): module to read the package from (default: 'app')

  • serial (string, optional): target device

  • force_stop (boolean): kill the app before starting, guaranteeing a cold start (default: false)

Returns: { "launched": boolean, "packageName": string, "serial": string }

Examples:

  • Use when: bringing an app to the foreground before taking a screenshot

  • Use when: you need a cold start to reproduce a launch-time bug -> force_stop=true

  • Don't use when: the app is not installed yet (use android_install)

Error Handling:

  • Reports when the package is not installed, rather than silently doing nothing

  • An app with no launcher activity cannot be started this way

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
moduleNoGradle module that produces the APK. Almost always 'app'.app
serialNoDevice serial from android_list_devices. Optional when exactly one device is connected; required when several are.
force_stopNoForce-stop the app first so the next start is cold.
package_nameNoApplication id to launch.
project_pathNoGradle root to resolve the package from.
Behavior5/5

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

Beyond the annotations (readOnlyHint=false, destructiveHint=false), the description discloses error behavior: it reports when the package is not installed and cannot start apps without a launcher activity. It also clarifies the effect of force_stop (guaranteeing a cold start). These are useful behavioral traits not captured in the annotations.

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

Conciseness4/5

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

The description is well-structured with sections for arguments, return value, examples, and error handling. It is longer than minimal but each section adds necessary information. The redundant parameter list mirrors the schema, but the added usage examples justify the length.

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

Completeness5/5

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

For a tool with no output schema, the description includes the return type and shape, error cases, and distinct usage examples. It covers the parameter semantics and edge cases (app not installed, no launcher activity) making it self-sufficient for an agent.

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

Parameters4/5

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

The input schema already describes all parameters (100% coverage). The description adds value by explaining the relationship between project_path and package_name (when one can be omitted) and giving a concrete example for package_name. This extra context slightly elevates it above the baseline of 3.

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 states 'Start an installed app's launcher activity' which is a specific verb+resource, clearly distinguishing it from sibling tools like android_install (install) and android_screenshot (capture screen). It also notes the optional force-stop capability, further clarifying scope.

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

Usage Guidelines5/5

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

Explicit 'Use when' and 'Don't use when' examples are provided, including a specific alternative (use android_install if not installed) and a use case for force_stop to reproduce a launch-time bug. This gives clear direction on when to choose this tool over siblings.

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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