rn-device-mcp

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Boot a simulator

ios_boot

Boots an iOS Simulator by UDID or device name, waits until it is ready, and brings Simulator.app to the front so you can continue testing.

Instructions

Boots a simulator by udid or name (e.g. 'iPhone 17 Pro'), waits until it is ready and brings Simulator.app to front.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "device": "<device>"
    },
    "name": "ios_boot"
  }
}

Input Schema

Name	Required	Description	Default
`device`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Nov 4, 2026

TDQS

A4.2/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only declare that this is a non-readOnly, non-destructive operation; the description adds real behavioral context on top: the call blocks until the simulator is ready and it brings Simulator.app to the front, a host-UI side effect an agent should know about. It stops short of describing failure modes (unknown udid/name, already-booted device).

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?

One sentence, front-loaded with the action, packing input format and observable behavior with no filler. Nothing here needs trimming or reordering.

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

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a one-parameter tool with no output schema and annotations already covering the safety profile, the description supplies everything essential to invoke it correctly: input forms, blocking semantics, and the UI side effect. Only edge-case behavior (already booted, invalid identifier) is left unstated.

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 single parameter has zero schema description coverage (bare string with minLength 1), so the description carries the burden and does it well: it explains the value can be a udid or a device name and gives a concrete example. It does not specify lookup/ambiguity rules if a name matches multiple devices.

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?

States a specific verb and resource ("Boots a simulator") plus the two accepted identifier forms and the post-boot behaviors (waits for readiness, foregrounds Simulator.app). This clearly separates it from siblings like ios_shutdown and ios_simulators without opening any schema.

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

Usage Guidelines3/5

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

Usage is implied by the operation itself — you boot before launching apps or taking screenshots — but there is no explicit when-to-use/when-not guidance and no mention of the sibling ios_shutdown or of what happens if the device is already booted.

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