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 specifies that the tool invokes a specific command ('xcrun simctl list --json'), which implies it's a read-only operation that fetches data. However, it lacks details on output format (e.g., JSON structure), error handling, or performance considerations like rate limits, leaving some behavioral traits unclear.

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 and implementation method. It is front-loaded with the core action and resource, with no wasted words or unnecessary details, making it highly concise and well-structured.

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 (0 parameters, no annotations, no output schema), the description is adequate but has gaps. It explains what the tool does and how it works, but without annotations or output schema, it misses details on behavioral traits like error handling or return format. For a read-only listing tool, this is minimally viable but could be more complete.

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 0 parameters with 100% schema description coverage, so the schema fully documents the lack of inputs. The description adds no parameter information, which is appropriate here. Baseline is 4 for 0 parameters, as no additional semantics are needed beyond what the schema already indicates.

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 specific action ('Lists all available iOS simulators') and the resource ('iOS simulators with their details'), including the exact command invoked ('xcrun simctl list --json'). It distinguishes itself from siblings like 'list_directory' or 'list_project_files' by focusing specifically on iOS simulators.

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 when needing to list iOS simulators, but does not explicitly state when to use this tool versus alternatives like 'run_xcrun' (which could run other commands) or other listing tools. No exclusions or prerequisites are mentioned, leaving usage context somewhat implied rather than clearly defined.

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