screen_size

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

The description discloses the internal behavior of taking a temporary screenshot and using sips to read dimensions, providing transparency beyond what annotations would cover. However, it does not mention potential side effects like temporary file creation or error conditions.

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 wasted words, efficiently conveying the tool's purpose and method.

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 tool with one parameter and no output schema, the description is largely complete, but it omits the prerequisite of the simulator being booted and details about the return format or units of the dimensions.

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 provides 100% coverage for the only parameter (udid) with a basic description. The description adds no additional meaning or context for the parameter beyond what the schema already provides, so it meets the 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?

The description clearly states the action ('returns'), the specific resource ('pixel dimensions of a booted iOS simulator screen'), and the method. It distinguishes this tool from siblings like 'screenshot' by specifying that it extracts dimensions rather than capturing an image.

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 description implies usage for getting screen dimensions but does not explicitly state when to use this tool versus alternatives (e.g., orientation_get). It lacks guidance on prerequisites (e.g., simulator must be booted) and exclusions.

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