xcode-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 core action ('Capture a screenshot') but lacks critical details: it doesn't specify if this requires simulator boot state, mention error conditions (e.g., if device isn't found), describe output handling (e.g., base64 format when output_path is omitted), or note any side effects. For a tool with no annotation coverage, this is a significant gap in transparency.

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 that directly states the tool's purpose without unnecessary words. It is front-loaded with the core action and resource, making it easy to parse. Every word earns its place, with no 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 the complexity (a screenshot tool with 4 parameters, no output schema, and no annotations), the description is incomplete. It doesn't explain the return behavior (e.g., base64 data when output_path is omitted), error handling, or dependencies like simulator state. For a tool that interacts with device state and has multiple options, more context is needed to guide effective 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?

Schema description coverage is 100%, so the schema fully documents all parameters (device, output_path, type, mask) with descriptions and enums. The description adds no parameter-specific information beyond what's in the schema. According to the rules, with high schema coverage (>80%), the baseline is 3 even with no param info in the description.

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 a screenshot') and target resource ('from a simulator'), which is specific and unambiguous. It distinguishes this tool from siblings like simctl_boot or simctl_install by focusing on visual capture rather than device management or app operations. However, it doesn't explicitly differentiate from potential similar tools (e.g., if there were a simctl_record_video), though none exist 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., the simulator must be running), exclusions (e.g., not for physical devices), or compare to other screenshot methods. This leaves the agent to infer usage from the tool name and context alone.

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