This project demonstrates the capabilities of App Functions, a new feature introduced in Android 16 (API level 36). App Functions allow applications to expose their functionalities to the Android system, enabling cross-app orchestration. By leveraging this framework, developers can integrate large language models (LLMs) to create agentic experiences with tool-calling capabilities.
This repository contains two sample applications that illustrate a function-calling workflow, using the androidx.appfunctions Jetpack library:
Agent App: Demonstrates how to discover functions registered by other apps, parse their declarations, and invoke them to retrieve results.
Tool App: Shows how to register and expose an app's own functions, making them available for other apps (like the Agent) to call.
Ensure the following flag is enabled on your device or emulator:
adb shell aflags list | grep "enable_app_functions_schema_parser"
If this flag is not set to enabled, you will need to modify the USE_CONTENT_PROVIDER variable to true in the following file: agent/src/main/java/dev/filipfan/appfunctionspilot/agent/MainViewModel.kt.
Note
Using USE_CONTENT_PROVIDER=true serves as a workaround for devices that don't support dynamic parsing. However, this method may return incomplete data, such as functions with missing descriptions. This fallback is intended to ensure basic functionality and reflects a limitation of the androidx.appfunctions library.
You can install the tool app directly using ADB:
adb install tool-debug.apk
The agent app requires the android.permission.EXECUTE_APP_FUNCTIONS permission, which is a protected permission granted only to privileged system applications. To install the agent app, you'll need a rooted device or emulator.
- Disable Permission Enforcement: First, modify the
build.propfile to disable privileged permission enforcement.
adb root
adb remount
adb shell "sed -i 's/ro.control_privapp_permissions=enforce/ro.control_privapp_permissions=log/g' /vendor/build.prop"
- Install as a Privileged App: Push the APK to the privileged apps directory, such as
/system/priv-app:
adb push agent-debug.apk /system/priv-app
adb reboot
Note
After the initial privileged installation, you can update the agent app using a standard adb install command, provided its permissions in the manifest do not change.