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simctl-mcp-server

simctl-mcp-server

by nzrsky
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

simctl_list_devices

Lists iOS simulators and their states. Filter by availability, device type, or iOS version, and output as JSON or text.

Instructions

List available iOS simulators and their states.

Args: format: Output format (json or text). Defaults to json. filter: Optional filter term (e.g., 'available', 'iPhone', 'iOS 17')

Returns: List of available simulators

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "simctl_list_devices"
  }
}

Input Schema

NameRequiredDescriptionDefault
formatNojson
filterNo

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A4/5.0
Behavior3/5

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

With no annotations, the description carries the full burden. It states 'list' and 'states', implying a read-only operation, but does not explicitly confirm non-destructiveness or mention side effects. The term 'available' is ambiguous without clarification of scope (all devices vs booted only).

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 extremely concise: a one-sentence purpose followed by clearly labeled Args and Returns sections. Every sentence adds value, and the purpose is front-loaded.

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?

Given the presence of an output schema, the description need not detail return structure, but it still mentions 'List of available simulators'. It lacks context about prerequisites (e.g., Xcode runtime) and what states entail, but is sufficient for an agent to understand the tool's role among action-oriented siblings.

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?

Schema coverage is 0%, so the description compensates by explaining format (json/text default) and filter (with examples). This adds useful meaning beyond the schema's type and defaults, though the exact allowed values for format could be more precise.

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 tool lists iOS simulators and their states, using a specific verb and resource. It is distinct from sibling tools which are all actions (boot, create, delete, etc.), making selection unambiguous.

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?

The description implies usage (e.g., before acting on a device) but does not explicitly state when to use or when not to use this tool. No alternatives or exclusions are mentioned, leaving guidance only implicit.

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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