Select the active Android device so all subsequent PreviewAPK commands target it. Pass a device name or ID from previewapk_list_devices.
Select your working device — the 'cd' of PreviewAPK. After selecting, every other tool talks to this device until you select another or start one (starting also selects). Pass the device NAME (e.g. 'Device 1') or its id, from previewapk_list_devices.
| Name | Required | Description | Default |
|---|---|---|---|
| device | Yes | device name or id |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden and does disclose the crucial stateful behavior: the selection persists across all other tools until changed or until a device is started. It does not say what happens if the device name is invalid or whether a confirmation is returned, so it stops short of full behavioral coverage.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three short sentences, front-loaded with the core purpose and analogy, then the stateful consequence, then the parameter source. No filler.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a one-parameter session-state tool with no annotations or output schema, the description covers purpose, persistence semantics, the competing 'start' path, and where to get the argument. Only failure/validation behavior is left unstated.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% (the single param is documented as 'device name or id'), so the baseline is 3; the description adds real value by giving the accepted format example ('Device 1') and the authoritative source for the value, previewapk_list_devices.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb and resource ('Select your working device') and pins down its role with the 'cd of PreviewAPK' analogy, which cleanly separates it from the action siblings (tap, swipe, screenshot) that merely consume the selection.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
Explicitly frames the tool as a prerequisite ('After selecting, every other tool talks to this device'), names the alternatives that also set state ('or start one — starting also selects'), and routes the agent to previewapk_list_devices for valid values.
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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