macOS GUI Control MCP

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the action ('Take a screenshot') but doesn't describe what happens after capture (e.g., where the screenshot is saved, format, permissions needed, or if it's interactive). For a tool with potential side effects and no annotation coverage, this is a significant 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 extremely concise with a single, clear sentence that front-loads the core purpose. Every word earns its place, with no redundant or vague phrasing. It efficiently communicates the tool's functionality without unnecessary detail.

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 complexity (capturing screen content with potential side effects), no annotations, no output schema, and incomplete behavioral details, the description is insufficient. It doesn't cover what the tool returns, error conditions, or practical usage constraints, leaving significant gaps for an AI agent.

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 description coverage is 100%, with the parameter 'region' documented as optional for capturing a specific area. The description adds minimal value beyond the schema by mentioning 'full screen or region', but doesn't explain coordinate systems, units, or default behavior when region is omitted. Baseline 3 is appropriate given high schema coverage.

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 tool's purpose with a specific verb ('Take') and resource ('screenshot'), specifying it can capture full screen or region. It distinguishes from siblings like screen_get_color or screen_get_size by focusing on capture rather than measurement. However, it doesn't explicitly differentiate from all siblings (e.g., run_applescript could also capture screenshots).

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 when screen_capture is preferred over other screen-related tools like screen_get_color or when to use it instead of shell commands via run_shell. There's no context about prerequisites, timing, or exclusions.

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