Xcode MCP Server

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 the action ('capture') but doesn't describe what happens during execution (e.g., whether it pauses the simulator, requires specific permissions, or has side effects). It also omits details like file format (e.g., PNG), error handling, or rate limits, leaving significant gaps for a tool that performs an I/O 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 zero wasted words. It's front-loaded with the core action and resource, making it immediately scannable. Every word earns its place by directly conveying the tool's function without redundancy or fluff.

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 no annotations, no output schema, and a 2-parameter tool with 100% schema coverage, the description is incomplete. It lacks behavioral details (e.g., what the screenshot looks like, error cases), usage context, and output information (e.g., success confirmation or file path validation). For a tool that captures media, this leaves too many unknowns for reliable agent invocation.

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 description coverage is 100%, with both parameters (device_id, output_path) clearly documented in the schema. The description adds no additional meaning beyond implying these are needed for the capture, which is already evident from the schema. This meets the baseline of 3 since the schema does the heavy lifting, but the description doesn't compensate with extra context like example values or constraints.

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 ('capture') and resource ('screenshot from simulator'), making the tool's purpose immediately understandable. It distinguishes from siblings like xcode_device_info or xcode_list_simulators by focusing on screenshot capture rather than information retrieval or listing. However, it doesn't specify what type of simulator (iOS, watchOS, etc.) or differentiate from potential media capture tools not in the sibling list.

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 (e.g., simulator must be running), when not to use it (e.g., for physical devices), or direct alternatives among siblings like xcode_device_info for status checks. Usage is implied only by the tool name and description, with no explicit context.

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