android-device-automation

Android Device Automation

CRITICAL RULES — VIOLATIONS WILL BREAK THE WORKFLOW:

1. Never run midscene commands in the background. Each command must run synchronously so you can read its output (especially screenshots) before deciding the next action. Background execution breaks the screenshot-analyze-act loop.
2. Run only one midscene command at a time. Wait for the previous command to finish, read the screenshot, then decide the next action. Never chain multiple commands together.
3. Allow enough time for each command to complete. Midscene commands involve AI inference and screen interaction, which can take longer than typical shell commands. A typical command needs about 1 minute; complex act commands may need even longer.
4. Always report task results before finishing. After completing the automation task, you MUST proactively summarize the results to the user — including key data found, actions completed, screenshots taken, and any relevant findings. Never silently end after the last automation step; the user expects a complete response in a single interaction.

Automate Android devices using npx -y @midscene/android@1. Each CLI command maps directly to an MCP tool — you (the AI agent) act as the brain, deciding which actions to take based on screenshots.

What act Can Do

Inside a single act call on Android, Midscene can tap, double-tap, long-press, type, clear text, scroll or swipe in any direction, pull to refresh, drag items, zoom with two fingers, press keys, and use system navigation such as Back, Home, or recent apps while working from the current visible screen.

Prerequisites

Midscene requires models with strong visual grounding capabilities. The following environment variables must be configured — either as system environment variables or in a .env file in the current working directory (Midscene loads .env automatically):

MIDSCENE_MODEL_API_KEY="your-api-key"
MIDSCENE_MODEL_NAME="model-name"
MIDSCENE_MODEL_BASE_URL="https://..."
MIDSCENE_MODEL_FAMILY="family-identifier"

Example: Gemini (Gemini-3-Flash)

MIDSCENE_MODEL_API_KEY="your-google-api-key"
MIDSCENE_MODEL_NAME="gemini-3-flash"
MIDSCENE_MODEL_BASE_URL="https://generativelanguage.googleapis.com/v1beta/openai/"
MIDSCENE_MODEL_FAMILY="gemini"

Example: Qwen 3.5

MIDSCENE_MODEL_API_KEY="your-aliyun-api-key"
MIDSCENE_MODEL_NAME="qwen3.5-plus"
MIDSCENE_MODEL_BASE_URL="https://dashscope.aliyuncs.com/compatible-mode/v1"
MIDSCENE_MODEL_FAMILY="qwen3.5"
MIDSCENE_MODEL_REASONING_ENABLED="false"
# If using OpenRouter, set:
# MIDSCENE_MODEL_API_KEY="your-openrouter-api-key"
# MIDSCENE_MODEL_NAME="qwen/qwen3.5-plus"
# MIDSCENE_MODEL_BASE_URL="https://openrouter.ai/api/v1"

Example: Doubao Seed 2.0 Lite

MIDSCENE_MODEL_API_KEY="your-doubao-api-key"
MIDSCENE_MODEL_NAME="doubao-seed-2-0-lite"
MIDSCENE_MODEL_BASE_URL="https://ark.cn-beijing.volces.com/api/v3"
MIDSCENE_MODEL_FAMILY="doubao-seed"

Commonly used models: Doubao Seed 2.0 Lite, Qwen 3.5, Zhipu GLM-4.6V, Gemini-3-Pro, Gemini-3-Flash.

If the model is not configured, ask the user to set it up. See Model Configuration for supported providers.

Commands

Common Android CLI Flags

Use these flags on commands that create or use the Android agent, such as connect, take_screenshot, act, assert, and tap:

• --device-id <id>: Target a specific Android device from adb devices.
• --use-scrcpy: Enable scrcpy accelerated screenshots. Use this when normal screenshot capture is slow or unstable. Because CLI invocations are stateless, pass this flag on each Android Midscene command where you want scrcpy-based screenshots.

Connect to Device

npx -y @midscene/android@1 connect
npx -y @midscene/android@1 connect --device-id emulator-5554
npx -y @midscene/android@1 connect --device-id emulator-5554 --use-scrcpy

Launch an App or URL

Use the dedicated launch step when you want a deterministic starting point before the rest of the task:

npx -y @midscene/android@1 launch --uri https://www.ebay.com
npx -y @midscene/android@1 launch --uri com.android.settings
npx -y @midscene/android@1 launch --uri com.android.settings/.Settings

Run a Raw Android Shell Command

Use this when the task needs lower-level device control that is not best expressed as a visible UI interaction:

npx -y @midscene/android@1 runadbshell --command "dumpsys battery"

This is forwarded to adb shell on the connected device. In practice, the underlying command is adb -s <deviceId> shell dumpsys battery and some environments may also include the default ADB server port, such as adb -P 5037 -s <deviceId> shell dumpsys battery.

Take Screenshot

npx -y @midscene/android@1 take_screenshot
npx -y @midscene/android@1 take_screenshot --device-id emulator-5554 --use-scrcpy

After taking a screenshot, read the saved image file to understand the current screen state before deciding the next action.

Perform Action

Use act to interact with the device and get the result. It autonomously handles all UI interactions internally — tapping, typing, scrolling, swiping, waiting, and navigating — so you should give it complex, high-level tasks as a whole rather than breaking them into small steps. Describe what you want to do and the desired effect in natural language:

# specific instructions
npx -y @midscene/android@1 act --prompt "type hello world in the search field and press Enter"
npx -y @midscene/android@1 act --prompt "long press the message bubble and tap Delete in the popup menu"
npx -y @midscene/android@1 act --device-id emulator-5554 --use-scrcpy --prompt "type hello world in the search field and press Enter"

# or target-driven instructions
npx -y @midscene/android@1 act --prompt "open Settings and navigate to Wi-Fi settings, tell me the connected network name"

Assert Current Screen State

Use assert to verify that the current screen satisfies a natural language condition. It does not perform UI actions; it checks the visible screen state and passes only when the assertion is true. Use this for validation, QA checks, and final state verification after act.

npx -y @midscene/android@1 assert --prompt "there is a login button visible"
npx -y @midscene/android@1 assert --prompt "the settings screen shows Wi-Fi and Bluetooth options"
npx -y @midscene/android@1 assert --device-id emulator-5554 --prompt "the app shows a successful login message"
npx -y @midscene/android@1 assert --device-id emulator-5554 --use-scrcpy --prompt "the app shows a successful login message"

By default a failed assertion throws an AI-generated reason. Pass --message to throw a custom error message instead, which is useful for surfacing the intended outcome in QA and CI logs.

npx -y @midscene/android@1 assert \
  --prompt "the order confirmation screen is visible" \
  --message "the order should be confirmed after tapping Pay"

When the assertion needs to compare against a reference image (icon, logo, screenshot), pass --image for the URL/path and --image-name for its display name. Each --image may be an http(s) link, a data: URI, or a local file path. Repeat both flags in matching order when you need to attach more than one image. Add --convertHttpImage2Base64 true when the model cannot reach the URL directly. Requires @midscene/[email protected]+.

npx -y @midscene/android@1 assert \
  --prompt "the visible app icon matches the supplied reference image" \
  --image "https://github.githubassets.com/assets/GitHub-Mark-ea2971cee799.png" \
  --image-name "icon" \
  --convertHttpImage2Base64 true

# or with a local file
npx -y @midscene/android@1 assert \
  --prompt "the header on screen matches the local screenshot" \
  --image "./fixtures/header.png" \
  --image-name "header"

# multiple reference images — pair --image and --image-name by order
npx -y @midscene/android@1 assert \
  --prompt "the screen shows both the app icon and the header" \
  --image "./fixtures/icon.png"   --image-name "icon" \
  --image "./fixtures/header.png" --image-name "header"

Use a Reference Image for Precise Targeting

When the user provides a screenshot, icon, logo, or reference image and wants an exact visual match, prefer tap --locate instead of a generic act --prompt. Pass --locate as JSON. The prompt describes the target, images supplies named reference images, and convertHttpImage2Base64: true is useful when the image URL may not be directly accessible to the model.

npx -y @midscene/android@1 tap --locate '{
  "prompt": "tap the area contains the image",
  "images": [
    {
      "name": "target image",
      "url": "https://github.githubassets.com/assets/GitHub-Mark-ea2971cee799.png"
    }
  ],
  "convertHttpImage2Base64": true
}'

The same locate JSON shape also works for other commands that accept a locate parameter.

Disconnect

npx -y @midscene/android@1 disconnect

Consume Report Files

The generated HTML report is recommended for human reading first. It includes step-by-step execution details and replay videos for each operation, which makes it much easier to understand what happened and troubleshoot problems.

If another skill or tool needs to consume the report, first convert it with report-tool from the same platform CLI package. Prefer Markdown for LLM-based workflows. Use JSON when the report needs to be processed programmatically.

npx -y @midscene/android@1 report-tool --action to-markdown --htmlPath ./midscene_run/report/.../index.html --outputDir ./output-markdown
npx -y @midscene/android@1 report-tool --action split --htmlPath ./midscene_run/report/.../index.html --outputDir ./output-data

Workflow Pattern

Since CLI commands are stateless between invocations, follow this pattern:

1. Connect to establish a session
2. Launch the target app and take screenshot to see the current state, make sure the app is launched and visible on the screen.
3. Execute action using act to perform the desired action or target-driven instructions, and use assert when you need to verify the resulting screen state.
4. Disconnect when done
5. Report results — summarize what was accomplished, present key findings and data extracted during the task, and list any generated files (screenshots, logs, etc.) with their paths

Best Practices

1. Bring the target app to the foreground before using this skill: For best efficiency, launch the app using ADB (e.g., adb shell am start -n <package/activity>) before invoking any midscene commands. Then take a screenshot to confirm the app is actually in the foreground. Only after visual confirmation should you proceed with UI automation using this skill. ADB commands are significantly faster than using midscene to navigate to and open apps.
2. Be specific about UI elements: Instead of vague descriptions, provide clear, specific details. Say "the Wi-Fi toggle switch on the right side" instead of "the toggle".
3. Describe locations when possible: Help target elements by describing their position (e.g., "the search icon at the top right", "the third item in the list").
4. Never run in background: Every midscene command must run synchronously — background execution breaks the screenshot-analyze-act loop.
5. Batch related operations into a single act command: When performing consecutive operations within the same app, combine them into one act prompt instead of splitting them into separate commands. For example, "open Settings, tap Wi-Fi, and toggle it on" should be a single act call, not three. This reduces round-trips, avoids unnecessary screenshot-analyze cycles, and is significantly faster.
6. Use scrcpy when screenshot capture needs acceleration: Add --use-scrcpy to each relevant command when normal Android screenshots are slow, flaky, or blocked by the environment.
7. Use assert for verification: When the goal is to confirm that a screen state is true, use assert --prompt "..." instead of an act prompt. Keep assertions observable and specific, such as "the permission dialog is visible" or "the Save button is disabled".
8. Always report results after completion: After finishing the automation task, you MUST proactively present the results to the user without waiting for them to ask. This includes: (1) the answer to the user's original question or the outcome of the requested task, (2) key data extracted or observed during execution, (3) screenshots and other generated files with their paths, (4) a brief summary of steps taken. Do NOT silently finish after the last automation command — the user expects complete results in a single interaction.
9. Prefer tap --locate when a reference image is provided: If the user shares a screenshot, icon, or logo and wants that exact visual target, use tap --locate with a multimodal locate JSON object such as { "prompt": "...", "images": [...] } instead of relying only on act --prompt.

Example — Popup menu interaction:

npx -y @midscene/android@1 act --prompt "long press the message bubble and tap Delete in the popup menu"
npx -y @midscene/android@1 take_screenshot

Example — Form interaction:

npx -y @midscene/android@1 act --prompt "fill in the username field with 'testuser' and the password field with 'pass123', then tap the Login button"
npx -y @midscene/android@1 take_screenshot

Improve Precision (Deep Locate / Deep Think)

Two optional global flags help when Midscene struggles with a task. Put them anywhere in the command (before or after the sub-command); once set, the relevant operations use them by default, so you don't pass a per-call parameter.

• --deep-locate — spends an extra round of visual reasoning to pinpoint the target element. Use it when an action interacts with the wrong spot (location drift / offset). It applies to every operation that locates an element, including tap --locate and the locating that happens inside act.
• --deep-think — plans act with deeper reasoning (richer context and sub-goal decomposition). Use it for complex, multi-step act instructions; it only affects planning.

Both trade a little speed for better results, and you can combine them.

# more accurate element location (helps act's internal locating too)
npx -y @midscene/android@1 act --deep-locate --prompt "tap the small overflow (⋮) icon in the top-right corner"

# deeper planning for a complex, multi-step act
npx -y @midscene/android@1 act --deep-think --prompt "open Settings, go to Wi-Fi, and connect to the network named Office"

# combine both
npx -y @midscene/android@1 act --deep-locate --deep-think --prompt "fill in the signup form and tap Submit"

Troubleshooting

Problem	Solution
ADB not found	Install Android SDK Platform Tools: brew install android-platform-tools (macOS) or download from developer.android.com.
Device not listed	Check USB connection, ensure USB debugging is enabled in Developer Options, and run adb devices.
Device shows "unauthorized"	Unlock the device and accept the USB debugging authorization prompt. Then run adb devices again.
Device shows "offline"	Disconnect and reconnect the USB cable. Run adb kill-server && adb start-server.
Command timeout	The device screen may be off or locked. Wake the device with adb shell input keyevent KEYCODE_WAKEUP and unlock it.
API key error	Check .env file contains MIDSCENE_MODEL_API_KEY=<your-key>. See Model Configuration.
@midscene/* dependency version is outdated	Check local versions with npm ls @midscene/android @midscene/core @midscene/shared (or pnpm why @midscene/android). Compare with latest versions using npm view @midscene/android version, npm view @midscene/core version, and npm view @midscene/shared version. Upgrade as needed (npm i @midscene/android@latest @midscene/core@latest @midscene/shared@latest).
Wrong device targeted	If multiple devices are connected, use the --device-id <id> flag.
Screenshots are slow or flaky	Add --use-scrcpy to the Android Midscene command to enable scrcpy accelerated screenshots.