Get the size and class of the key window on an iOS device for UI inspection and automation.
Key window size: {width,height,x,y,cx,cy,className}. Safe on TikTok.
This tool declares no required parameters. Add optional parameters from the input schema as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {},
"name": "screen_window"
}
}| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full burden. It discloses the output fields (width, height, x, y, cx, cy, className) and states it is 'safe on TikTok', implying no destructive side effects. This adds useful behavioral context beyond the empty schema.
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?
The description is very concise: one sentence with key information. However, it could be slightly clearer with a verb, but it earns its place without waste.
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?
Given the tool has no parameters and no output schema, the description is somewhat complete for a simple retrieval tool. However, it lacks an action verb and does not explain what the tool actually does (e.g., 'reads the current window size'). The safety hint is helpful but incomplete.
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?
There are zero parameters, so baseline is 4. The description does not need to explain parameters but instead describes the output. It adds meaning by listing the fields that the tool returns, which is helpful.
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?
The description implies the tool retrieves window size but lacks an explicit verb like 'get' or 'retrieve'. The fields listed hint at the output, but the purpose is not fully stated. It distinguishes from siblings like screen_snapshot or screen_search by focusing on dimensions, but not explicitly.
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?
No when-to-use or when-not-to-use guidance is provided. The phrase 'Safe on TikTok' hints at a safety condition but does not clarify when to prefer this tool over alternatives like screen_snapshot or tap.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.