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boot_sim

Start an iOS simulator by providing its UUID to enable testing and development of iOS applications.

Instructions

Boots an iOS simulator. IMPORTANT: You MUST provide the simulatorUuid parameter. Example: boot_sim({ simulatorUuid: 'YOUR_UUID_HERE' })

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
simulatorUuidYesUUID of the simulator to use (obtained from list_simulators)

Implementation Reference

  • The core handler function for the 'boot_sim' tool. Validates the simulatorUuid parameter, executes 'xcrun simctl boot' command, handles success/error responses, and provides next-step instructions.
        async (params): Promise<ToolResponse> => {
          const simulatorUuidValidation = validateRequiredParam('simulatorUuid', params.simulatorUuid);
          if (!simulatorUuidValidation.isValid) {
            return simulatorUuidValidation.errorResponse!;
          }
    
          log('info', `Starting xcrun simctl boot request for simulator ${params.simulatorUuid}`);
    
          try {
            const command = ['xcrun', 'simctl', 'boot', params.simulatorUuid];
            const result = await executeCommand(command, 'Boot Simulator');
    
            if (!result.success) {
              return {
                content: [
                  {
                    type: 'text',
                    text: `Boot simulator operation failed: ${result.error}`,
                  },
                ],
              };
            }
    
            return {
              content: [
                {
                  type: 'text',
                  text: `Simulator booted successfully. Next steps:
    1. Open the Simulator app: open_sim({ enabled: true })
    2. Install an app: install_app_sim({ simulatorUuid: "${params.simulatorUuid}", appPath: "PATH_TO_YOUR_APP" })
    3. Launch an app: launch_app_sim({ simulatorUuid: "${params.simulatorUuid}", bundleId: "YOUR_APP_BUNDLE_ID" })
    4. Log capture options:
       - Option 1: Capture structured logs only (app continues running):
         start_sim_log_cap({ simulatorUuid: "${params.simulatorUuid}", bundleId: "YOUR_APP_BUNDLE_ID" })
       - Option 2: Capture both console and structured logs (app will restart):
         start_sim_log_cap({ simulatorUuid: "${params.simulatorUuid}", bundleId: "YOUR_APP_BUNDLE_ID", captureConsole: true })
       - Option 3: Launch app with logs in one step:
         launch_app_logs_sim({ simulatorUuid: "${params.simulatorUuid}", bundleId: "YOUR_APP_BUNDLE_ID" })`,
                },
              ],
            };
          } catch (error) {
            const errorMessage = error instanceof Error ? error.message : String(error);
            log('error', `Error during boot simulator operation: ${errorMessage}`);
            return {
              content: [
                {
                  type: 'text',
                  text: `Boot simulator operation failed: ${errorMessage}`,
                },
              ],
            };
          }
  • Input schema using Zod for the 'boot_sim' tool, defining the required 'simulatorUuid' string parameter.
      simulatorUuid: z
        .string()
        .describe('UUID of the simulator to use (obtained from list_simulators)'),
    },
  • Local registration function that registers the 'boot_sim' tool on the MCP server, including name, description, input schema, and handler.
    export function registerBootSimulatorTool(server: McpServer): void {
      server.tool(
        'boot_sim',
        "Boots an iOS simulator. IMPORTANT: You MUST provide the simulatorUuid parameter. Example: boot_sim({ simulatorUuid: 'YOUR_UUID_HERE' })",
        {
          simulatorUuid: z
            .string()
            .describe('UUID of the simulator to use (obtained from list_simulators)'),
        },
        async (params): Promise<ToolResponse> => {
          const simulatorUuidValidation = validateRequiredParam('simulatorUuid', params.simulatorUuid);
          if (!simulatorUuidValidation.isValid) {
            return simulatorUuidValidation.errorResponse!;
          }
    
          log('info', `Starting xcrun simctl boot request for simulator ${params.simulatorUuid}`);
    
          try {
            const command = ['xcrun', 'simctl', 'boot', params.simulatorUuid];
            const result = await executeCommand(command, 'Boot Simulator');
    
            if (!result.success) {
              return {
                content: [
                  {
                    type: 'text',
                    text: `Boot simulator operation failed: ${result.error}`,
                  },
                ],
              };
            }
    
            return {
              content: [
                {
                  type: 'text',
                  text: `Simulator booted successfully. Next steps:
    1. Open the Simulator app: open_sim({ enabled: true })
    2. Install an app: install_app_sim({ simulatorUuid: "${params.simulatorUuid}", appPath: "PATH_TO_YOUR_APP" })
    3. Launch an app: launch_app_sim({ simulatorUuid: "${params.simulatorUuid}", bundleId: "YOUR_APP_BUNDLE_ID" })
    4. Log capture options:
       - Option 1: Capture structured logs only (app continues running):
         start_sim_log_cap({ simulatorUuid: "${params.simulatorUuid}", bundleId: "YOUR_APP_BUNDLE_ID" })
       - Option 2: Capture both console and structured logs (app will restart):
         start_sim_log_cap({ simulatorUuid: "${params.simulatorUuid}", bundleId: "YOUR_APP_BUNDLE_ID", captureConsole: true })
       - Option 3: Launch app with logs in one step:
         launch_app_logs_sim({ simulatorUuid: "${params.simulatorUuid}", bundleId: "YOUR_APP_BUNDLE_ID" })`,
                },
              ],
            };
          } catch (error) {
            const errorMessage = error instanceof Error ? error.message : String(error);
            log('error', `Error during boot simulator operation: ${errorMessage}`);
            return {
              content: [
                {
                  type: 'text',
                  text: `Boot simulator operation failed: ${errorMessage}`,
                },
              ],
            };
          }
        },
      );
    }
  • Global tool registration configuration for 'boot_simulator' tool, imported from simulator.ts and enabled via environment variable.
      register: registerBootSimulatorTool,
      groups: [ToolGroup.SIMULATOR_MANAGEMENT, ToolGroup.IOS_SIMULATOR_WORKFLOW],
      envVar: 'XCODEBUILDMCP_TOOL_BOOT_SIMULATOR',
    },
Behavior2/5

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 mentions the required parameter but does not describe what 'booting' entails (e.g., whether it starts a virtual device, requires specific permissions, has side effects like resource consumption, or what happens on failure). This leaves significant 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 efficiently structured with two sentences: the first states the purpose, and the second provides critical usage guidance with an example. Every sentence earns its place, and it is front-loaded with essential information without unnecessary details.

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 moderate complexity (single parameter, no output schema, no annotations), the description is adequate but incomplete. It covers the basic purpose and parameter requirement but lacks details on behavioral aspects like what 'booting' involves, potential errors, or dependencies, leaving room for improvement in context.

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

Parameters3/5

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

The schema description coverage is 100%, so the schema already documents the simulatorUuid parameter fully. The description adds minimal value by emphasizing the parameter's necessity and providing an example, but does not add meaning beyond what the schema provides, aligning with the baseline score for high schema coverage.

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

Purpose5/5

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

The description clearly states the specific action ('Boots') and resource ('an iOS simulator'), distinguishing it from sibling tools like 'open_sim' or 'list_sims'. It precisely communicates the tool's function without ambiguity.

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

Usage Guidelines4/5

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

The description provides clear context by specifying that the simulatorUuid must be obtained from 'list_simulators', which implicitly guides when to use this tool. However, it does not explicitly state when to use alternatives like 'open_sim' or 'launch_app_sim', missing explicit exclusions or comparisons.

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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