mobile_get_screen_sizeRetrieve the pixel width and height of a specified mobile device to calculate UI coordinates, layouts, and interaction positions accurately.
Get the screen size of the mobile device in pixels
| Name | Required | Description | Default |
|---|---|---|---|
| device | Yes | The device identifier to use. Use mobile_list_available_devices to find which devices are available to you. |
Changes observed during successful MCP inspections.
v0.0.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=false, capping the need for safety disclosure. The description adds the output unit (pixels) and scope ('mobile device'), but says nothing about return format, orientation caveats, or whether values change with rotation.
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?
A single front-loaded sentence with zero waste. The unit, which is the most important qualifier, is placed at the end where it naturally qualifies 'size'.
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 read-only tool with full schema coverage and annotations, the definition is sufficient to invoke correctly. The only missing piece is whether the returned size is in physical or logical pixels and whether it reflects current orientation.
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% and the device parameter is fully documented (including a pointer to mobile_list_available_devices). The description adds no parameter meaning beyond the schema baseline.
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 (Get) and resource (screen size) with the unit ('in pixels'), distinguishing it from siblings like mobile_get_orientation. An agent knows exactly what this returns without checking the schema.
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 guidance, no mention of prerequisites, and no reference to alternatives. The schema's device description points to mobile_list_available_devices, but the prose itself offers nothing about when this tool is appropriate.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.