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open_sim

Launch the iOS Simulator directly from the XcodeBuildMCP server for testing and development purposes.

Instructions

Opens the iOS Simulator app.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault

No arguments

Implementation Reference

  • The core handler function `open_simLogic` that implements the tool logic by executing the macOS shell command `open -a Simulator` to launch the iOS Simulator app. It handles success with helpful next steps and errors gracefully.
    export async function open_simLogic(
      params: OpenSimParams,
      executor: CommandExecutor,
    ): Promise<ToolResponse> {
      log('info', 'Starting open simulator request');
    
      try {
        const command = ['open', '-a', 'Simulator'];
        const result = await executor(command, 'Open Simulator', true);
    
        if (!result.success) {
          return {
            content: [
              {
                type: 'text',
                text: `Open simulator operation failed: ${result.error}`,
              },
            ],
          };
        }
    
        return {
          content: [
            {
              type: 'text',
              text: `Simulator app opened successfully`,
            },
            {
              type: 'text',
              text: `Next Steps:
    1. Boot a simulator if needed: boot_sim({ simulatorId: 'UUID_FROM_LIST_SIMULATORS' })
    2. Launch your app and interact with it
    3. Log capture options:
       - Option 1: Capture structured logs only (app continues running):
         start_sim_log_cap({ simulatorId: 'UUID', bundleId: 'YOUR_APP_BUNDLE_ID' })
       - Option 2: Capture both console and structured logs (app will restart):
         start_sim_log_cap({ simulatorId: 'UUID', bundleId: 'YOUR_APP_BUNDLE_ID', captureConsole: true })
       - Option 3: Launch app with logs in one step:
         launch_app_logs_sim({ simulatorId: 'UUID', bundleId: 'YOUR_APP_BUNDLE_ID' })`,
            },
          ],
        };
      } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        log('error', `Error during open simulator operation: ${errorMessage}`);
        return {
          content: [
            {
              type: 'text',
              text: `Open simulator operation failed: ${errorMessage}`,
            },
          ],
        };
      }
    }
  • Zod schema for the `open_sim` tool parameters. No parameters are required (empty object).
    const openSimSchema = z.object({});
  • Default export registering the `open_sim` tool with name, description, schema, and wrapped handler for MCP compatibility.
    export default {
      name: 'open_sim',
      description: 'Opens the iOS Simulator app.',
      schema: openSimSchema.shape, // MCP SDK compatibility
      handler: createTypedTool(openSimSchema, open_simLogic, getDefaultCommandExecutor),
    };
  • Re-export of the `open_sim` tool default export for use in the simulator-management module.
    export { default } from '../simulator/open_sim.ts';
Behavior2/5

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 ('Opens') but doesn't describe what 'Opens' entails (e.g., launches the app, brings it to foreground, requires specific permissions, or has side effects like starting a simulator session). This leaves gaps in understanding the tool's behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, direct sentence with zero waste, front-loading the core action. It's appropriately sized for a simple tool with no parameters, making it easy to scan and understand immediately.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

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 output schema, no annotations), the description is minimally adequate but lacks context. It doesn't explain what happens after opening (e.g., success indicators, error conditions, or integration with sibling tools), leaving the agent with incomplete information for effective use in a broader workflow.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has 0 parameters with 100% coverage, meaning no parameters are documented in the schema. The description doesn't add parameter details, which is appropriate since there are none to explain. A baseline of 4 is applied as it adequately handles the lack of parameters without unnecessary elaboration.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the action ('Opens') and the target resource ('the iOS Simulator app'), providing a specific verb+resource combination. However, it doesn't explicitly differentiate from sibling tools like 'boot_sim' or 'launch_app_sim', which might have overlapping functionality in the simulator context.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is provided on when to use this tool versus alternatives. The description doesn't mention prerequisites (e.g., whether the simulator must be installed or running), exclusions, or comparisons to related tools like 'boot_sim' for starting the simulator or 'launch_app_sim' for launching apps within it.

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

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