---
name: appfunctions
description: Use when discovering, implementing, documenting, or testing Android App Functions (androidx.appfunctions) that expose app capabilities to on-device AI agents like Gemini. Triggered by phrases like "add an app function", "implement AppFunctions", "expose this as an app function", "discover app function candidates", "write KDoc for an app function", "optimize for MCP", "test app functions with adb", "list app functions", "invoke an app function".
---

# App Functions

Adapted from the official [Android App Functions skill](https://github.com/android/skills/tree/main/device-ai/appfunctions)
(Apache License 2.0). `core:app-functions` is this repo's implementation — read its
[`AGENTS.md`](../../../core/app-functions/AGENTS.md) first for the concrete module, service, and
KDoc-exception rules before applying the general guidance below.

Analyzes Android apps to identify key user workflows for AppFunctions such as creating a note,
playing media, or sending an automated or AI agent triggered message, voice commands, or system
shortcuts, without needing to open the app UI.

Generates Kotlin code to expose these workflows to the Android system, allowing agents to discover
and execute them on-device.

Also refines KDoc documentation to ensure AI agents correctly understand and use the provided
functionality.

## Prerequisites

The app must **`targetSdk 36`** or newer and use **`compileSdk 37`** or newer as AppFunctions, part
of the Android platform API, are available from Android 16 onwards. Always use the Jetpack library
(`androidx.appfunctions`) because it handles backward compatibility — the manifest component itself
stays inert (never bound) on older platforms as long as it's `@RequiresApi(36)` /
`tools:targetApi="36"`, so a module with a lower `minSdk` does not need a runtime SDK check.

## Workflows

This skill enables the caller to discover features that will be provided to system agents,
implement these with AppFunctions, improve function description for agents, and use ADB commands
for local evaluation and testing.

The full AppFunction development flow consists of these four steps:

- *[Step 1: Discovery](references/feature-discovery-analysis.md)*: Analyze Android codebases to identify and recommend potential AppFunctions. Use this step when a user asks to "discover AppFunctions," "find features for AI," or "analyze my app for agentic tools."
- *[Step 2: Implementation and configuration](references/implementation-configuration.md)*: Generate Kotlin implementations of AppFunctions, manage system-wide configuration, and configure build dependencies. Use this step when a user asks to "implement AppFunctions," "set up the AppFunctions framework," or "configure Hilt for AppFunctions."
- *[Step 3: KDoc refinement](references/kdoc-refinement-optimization.md)*: Optimize AppFunction KDoc for AI agents and Model Context Protocol. If a user asks to "write KDoc", "optimize for MCP", or "refactor tool descriptions for LLMs", use this step.
- *[Step 4: Testing and debugging](references/adb-interaction-testing.md)*: Provide commands to interact with AppFunctions using ADB for testing and debugging. If a user wants to "list app functions", "invoke an app function", or "verify app function registration" on a device, use this step.

If users request a subset of steps, you must encourage them to use all steps.

If they apply, you must load the following references:

- *[Context and terminology](references/context.md)*: Defines the ubiquitous language, architecture definitions, and design patterns across the AppFunctions skill suite. Load when you need to understand core architecture terminology or check the distinctions between modern and legacy AppFunctions APIs.
- *[Migration to service entry point](references/migrate-to-service-entry-point.md)* : Documents the systematic procedure for migrating Android applications using AppFunctions versions 1.0.0-alpha09 and lower to `AppFunctionServiceEntryPoint` architecture introduced in version 1.0.0-alpha10. Load when a user asks to migrate or upgrade existing AppFunctions code, or when you encounter legacy `AppFunctionConfiguration.Provider` implementations.

## Critical constraints

- **Modular consistency**: You must refine KDocs immediately after you generate AppFunction implementations.
- **Security**: Don't expose sensitive data or run destructive actions without user confirmation.
- **This repo's KDoc rule**: outside `core:app-functions`'s `@AppFunction`/`@AppFunctionSerializable`
  declarations, this repo never writes comments or KDoc. Do not let AppFunction-style documentation
  leak into other modules.
- **Multi-module aggregation**: only the `app` module sets
  `ksp { arg("appfunctions:aggregateAppFunctions", "true") }`; a module that only declares
  `@AppFunction`s needs the `appfunctions` runtime + compiler dependencies but not that argument —
  see `core:app-functions/build.gradle.kts` and `app/build.gradle.kts`.

## Troubleshooting

- If you encounter build-time errors such as Kotlin Symbol Processing (KSP) issues, see [Implementation and configuration](references/implementation-configuration.md).
- If you encounter runtime errors such as missing services or execution failures, see [Testing and debugging](references/adb-interaction-testing.md).
- If you need architecture definitions and vocabulary, see [Context and terminology](references/context.md).
- If you encounter issues when upgrading legacy configurations, see [Migration to service entry point](references/migrate-to-service-entry-point.md).