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rahulkr

Enhanced ADB MCP Server

by rahulkr
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Python
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get_ui_hierarchy

Dump the complete UI hierarchy as XML to show all visible elements, their properties, bounds, and content descriptions for Android device inspection.

Instructions

Dump the complete UI hierarchy as XML. Shows all visible elements, their properties, bounds, and content descriptions.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
device_serialNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Implementation Reference

  • src/adb_mcp_server/server.py:247-256 (handler)
    The handler function for the 'get_ui_hierarchy' tool, decorated with @mcp.tool() for automatic registration in the FastMCP server. It dumps the UI hierarchy using ADB uiautomator, reads the XML file, cleans up, and returns the XML string.
    @mcp.tool()
def get_ui_hierarchy(device_serial: str | None = None) -> str:
    """
    Dump the complete UI hierarchy as XML.
    Shows all visible elements, their properties, bounds, and content descriptions.
    """
    run_adb(["shell", "uiautomator", "dump", "/sdcard/ui_dump.xml"], device_serial)
    output = run_adb(["shell", "cat", "/sdcard/ui_dump.xml"], device_serial)
    run_adb(["shell", "rm", "/sdcard/ui_dump.xml"], device_serial)
    return output

Tool Definition Quality

B3.1/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions that the tool dumps the UI hierarchy as XML with details on elements, but fails to describe critical behaviors such as performance impact, permissions required, whether it works on locked screens, or error handling. This leaves significant gaps in understanding how the tool operates.

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 is extremely concise and front-loaded, consisting of two sentences that directly state the tool's function and output details without any unnecessary words. Every sentence earns its place by providing essential information efficiently.

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?

Given the tool's complexity (dumping UI hierarchy) and the presence of an output schema, the description is minimally adequate but incomplete. It explains what the tool does but lacks context on usage, behavioral traits, and parameter meaning, which are crucial for effective tool selection and invocation by an AI agent.

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?

The input schema has one parameter ('device_serial') with 0% description coverage, and the tool description does not mention any parameters. Since there is only one parameter, the baseline is 4, but the description adds no semantic information about what 'device_serial' means or when to use it, reducing the score to 3 due to the lack of compensatory detail.

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

Purpose4/5

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

The description clearly states the tool's purpose with a specific verb ('Dump') and resource ('complete UI hierarchy as XML'), explaining it shows visible elements with their properties, bounds, and content descriptions. However, it does not explicitly differentiate from sibling tools like 'get_accessibility_info' or 'get_all_text_on_screen', which might offer overlapping functionality, leaving some ambiguity.

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

Usage Guidelines2/5

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

The description provides no guidance on when to use this tool versus alternatives. It lacks context on prerequisites, such as device connectivity or app state, and does not mention any exclusions or recommended scenarios, leaving the agent to infer usage based on the purpose alone.

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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