Expo iOS Development MCP Server

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ui.wait_for

Wait for UI elements to appear or become visible in iOS Simulator during React Native/Expo testing, ensuring reliable automation by specifying selectors and timeout settings.

Instructions

Wait for an element to be visible or exist

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": {
      "selector": "<selector>"
    },
    "name": "ui.wait_for"
  }
}

Input Schema

Name	Required	Description
`selector`	Yes	Element selector to wait for.
`visible`	No	Wait for visibility (true) or existence (false).
`timeout`	No	Timeout in milliseconds.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Jan 4, 2026

TDQS

C2.9/5.0

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. It mentions waiting for visibility or existence but lacks details on behavior: e.g., whether it polls continuously, returns on success/failure, throws errors on timeout, or interacts with the UI state. This is a significant gap for a tool with potential side effects.

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, efficient sentence with zero waste. It's front-loaded and directly conveys the core functionality without unnecessary elaboration, making it easy to parse quickly.

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

Completeness2/5

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

Given no annotations and no output schema, the description is incomplete. It doesn't explain return values (e.g., success/failure indicators), error handling, or dependencies (e.g., requiring a UI session). For a tool that interacts with dynamic UI elements, this leaves critical gaps for an agent.

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?

Schema description coverage is 100%, so the schema fully documents the parameters (selector, visible, timeout). The description adds no additional meaning beyond what's in the schema, such as examples or edge cases. Baseline 3 is appropriate since the schema does the heavy lifting.

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 tool's purpose with a specific verb ('wait for') and resource ('an element'), specifying the condition ('to be visible or exist'). It doesn't distinguish from siblings like ui.assert_text or ui.tap, which have different purposes, but the core functionality is well-defined.

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 explicit guidance on when to use this tool versus alternatives is provided. The description implies usage for waiting on UI elements, but it doesn't mention prerequisites (e.g., needing an active session) or compare it to siblings like ui.assert_text (which might assert without waiting).

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