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Press key

press_key

Press hardware/system keys like back, home, or enter on Android and iOS devices to trigger system actions during UI testing.

Instructions

Press a hardware/system key. Android: back, home, enter, tab, delete, search, menu, volume_up, volume_down, app_switch, power. iOS: enter, delete, tab, space, escape, home, lock, siri.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "device_id": "<device_id>",
      "key": "<key>"
    },
    "name": "press_key"
  }
}

Input Schema

Name	Required	Description	Default
`key`	Yes	Key name (e.g. 'back', 'enter', 'home')
`observe`	No	What to return after the action: 'screen' = fresh compact hierarchy, 'diff' = only what changed since last inspect, 'screenshot' = PNG, 'none' = just confirm.	screen
`device_id`	Yes	Device id from list_devices (adb serial like 'emulator-5554', or an iOS simulator UDID)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.2.0Jul 31, 2026

TDQS

A4.2/5.0

Behavior3/5

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

There are no annotations, so the description carries the burden. It discloses supported keys per platform but does not describe behavioral details such as return values, side effects, or prerequisites beyond what the input schema already states.

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?

Two sentences, front-loaded with the action, then the key list. No filler.

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

Completeness4/5

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

The tool is simple, all parameters are documented in the schema, and the description provides the necessary scope. It could benefit from mentioning the observe parameter's effect on return, but the schema covers it. No output schema exists, but the observe parameter addresses return.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, and the description adds value by listing the full set of valid key values per platform, which goes beyond the schema's generic example. The observe parameter is not mentioned, but schema covers it.

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

Purpose5/5

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

The description clearly states 'Press a hardware/system key' with a specific verb and resource, and it enumerates platform-specific supported keys, distinguishing it from sibling tools like input_text or tap.

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

Usage Guidelines4/5

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

The description provides clear context for when to use the tool by listing valid keys for Android and iOS, implying it is for system/hardware key presses. However, it does not explicitly mention alternatives or exclusions (e.g., for text input).

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.