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rahulkr
by rahulkr

double_tap

Tap twice at specified screen coordinates on Android devices for UI testing, app interaction, or gesture simulation during development workflows.

Instructions

Double tap at coordinates

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
xYes
yYes
device_serialNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Implementation Reference

  • Registers the double_tap tool using the FastMCP decorator
    @mcp.tool()
  • The handler function that performs a double tap at the given (x, y) coordinates on the specified device by executing two ADB input tap commands with a short delay between them.
    def double_tap(x: int, y: int, device_serial: str | None = None) -> str:
        """Double tap at coordinates"""
        run_adb(["shell", "input", "tap", str(x), str(y)], device_serial)
        time.sleep(0.1)
        run_adb(["shell", "input", "tap", str(x), str(y)], device_serial)
        return f"Double tapped at ({x}, {y})"
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 the action ('double tap') but lacks details on effects (e.g., whether it triggers UI events, requires specific app states, or has side effects), permissions, or error handling. This is inadequate for a mutation tool with zero annotation coverage.

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 ('Double tap at coordinates') with no wasted words, making it front-loaded and easy to parse. It efficiently conveys the core action in a single phrase.

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

Completeness2/5

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

Given the tool's complexity (a mutation action with 3 parameters, 0% schema coverage, no annotations, but an output schema), the description is insufficient. It lacks details on behavior, parameter meanings, usage context, and expected outcomes, making it incomplete for effective agent use despite the output schema.

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?

Schema description coverage is 0%, so the description must compensate for undocumented parameters. It implies coordinates (x, y) but doesn't explain units, coordinate system, or the optional 'device_serial' parameter. The description adds minimal value beyond the schema, failing to fully address the coverage gap.

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 'Double tap at coordinates' clearly states the action (double tap) and target (coordinates), which is specific and unambiguous. It distinguishes from siblings like 'tap' (single tap) and 'long_press', though it doesn't explicitly mention this differentiation. The purpose is not tautological with the name 'double_tap'.

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 like 'tap' or 'long_press', nor does it mention any prerequisites, context, or exclusions. It merely states what the tool does without indicating appropriate scenarios or constraints.

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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