Get Screen Size

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

The readOnlyHint annotation already communicates that this is a safe read operation. The description adds the 'in pixels' unit, which is helpful, but it does not disclose the return shape (e.g., width and height values) despite there being no output schema to fill that gap.

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 a single sentence with no filler or redundant phrasing. It states the operation, target, and unit efficiently, earning its place without excess words.

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 simple one-parameter, read-only getter, the description is largely complete: the parameter is fully documented in the schema and the annotations cover the safety profile. The only minor gap is the exact return format, which is relevant because no output schema is provided.

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?

The schema already provides 100% coverage for the single 'device' parameter and even instructs the agent to use mobile_list_available_devices. The description itself adds no parameter-level meaning, but the baseline of 3 applies because the schema carries the full burden successfully.

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 uses a specific verb ('Get'), a clear resource ('screen size'), and a precise unit ('in pixels'). It is unambiguous and distinguishes itself from related siblings like mobile_get_orientation, which concern a different device property.

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?

The intended use is clear: call this tool when the agent needs the mobile device's screen dimensions. There are no meaningful alternatives among the siblings for this exact purpose, so explicit exclusions are unnecessary, though the description does not explicitly state when not to use it.

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