macOS GUI Control MCP

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states what the tool does ('Get main screen dimensions') but doesn't describe how it behaves—such as whether it returns pixels, inches, or other units; if it's read-only (implied but not stated); or any performance or permission considerations. This leaves significant gaps for an agent to understand the tool's operation.

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, efficient sentence with no wasted words. It's front-loaded with the core action and resource, making it easy to parse quickly. Every word earns its place by directly contributing to understanding the tool's purpose.

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's simplicity (zero parameters, no output schema, no annotations), the description is minimally adequate. It states what the tool does but lacks details on return values (e.g., format, units) or behavioral context, which would be helpful for an agent to use it effectively. Without annotations or output schema, more completeness is needed for optimal use.

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 tool has zero parameters, and the input schema has 100% description coverage (though empty). The description doesn't need to add parameter information, so it meets the baseline for a parameterless tool. No additional semantic value is required or provided.

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 'Get main screen dimensions' clearly states the verb ('Get') and resource ('main screen dimensions'), making the purpose immediately understandable. However, it doesn't differentiate from sibling tools like 'screen_capture' or 'screen_get_color' beyond the obvious difference in what's being retrieved.

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 provides no guidance on when to use this tool versus alternatives. It doesn't mention prerequisites, timing considerations, or when other tools might be more appropriate, such as using 'mouse_get_position' for coordinate-based tasks or 'window_list' for window-specific dimensions.

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