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start_emulator

Launch an Android emulator by specifying its name to begin testing mobile applications in a virtual environment.

Instructions

Start an Android Emulator by name

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
emulator_nameYes

Implementation Reference

  • Handler function decorated with @mcp.tool(), which registers the tool and implements starting an Android emulator using subprocess.Popen with the emulator -avd command.
    @mcp.tool()
    def start_emulator(emulator_name: str) -> str:
        """Start an Android Emulator by name"""
        result = subprocess.Popen(
            ["emulator", "-avd", emulator_name],
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        return f"Emulator '{emulator_name}' is starting."
Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the action but lacks details on what 'Start' entails (e.g., does it launch a GUI, run in background, require specific permissions, have side effects like resource consumption, or return status?). This leaves significant gaps for an agent to understand the tool's behavior.

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 a single, direct sentence with zero wasted words, making it highly concise and front-loaded. Every word contributes to stating the tool's purpose efficiently.

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 operation with no annotations, no output schema, and low parameter coverage), the description is insufficient. It doesn't cover behavioral aspects like what happens on success/failure, prerequisites, or output expectations, leaving the agent with inadequate context for reliable use.

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 schema description coverage is 0%, so the description must compensate, but it only vaguely references 'by name' without explaining what constitutes a valid emulator name (e.g., format, source like AVD list, case sensitivity). This adds minimal meaning beyond the schema's basic parameter title, resulting in an adequate but incomplete baseline score.

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 action ('Start') and the resource ('Android Emulator by name'), making the purpose immediately understandable. However, it doesn't differentiate this tool from sibling tools like 'kill_emulator' or 'list_emulators' beyond the obvious verb difference, which prevents a perfect score.

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 doesn't mention prerequisites (e.g., whether an emulator must be installed or stopped first), exclusions, or relationships to sibling tools like 'kill_emulator' or 'list_emulators' for context.

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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