ios-mcp

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ios_set_value

Destructive

Set switches, sliders, and picker wheels to a specified value, checking current state first to avoid unintended toggles. Works for on/off, percentages, or exact wheel options.

Instructions

Set a switch, slider, or picker wheel to a value.

'on' or 'off' for a switch, a percentage such as '40%' or a fraction for a slider, and the option spelled the way the wheel spells it for a picker. A wheel is turned a row at a time and read back after each one, so an option it does not contain fails listing what it does.

Prefer this over tapping a switch: it checks the current state first, so asking for 'on' when it is already on does nothing rather than turning it off.

Steppers and segmented controls are not set this way. iOS reports their parts and the digest shows them, so tap 'Increment', 'Decrement', or the segment by its own label.

Input Schema

TableJSON Schema

Name	Required	Description
`ref`	No	A ref from the last observation, such as 'e7'. Preferred.
`value`	Yes	'on'/'off' for switches, otherwise the value.
`target`	No	Plain description of the element, e.g. 'the Send button'. Used if no ref.
`approve`	No	Signature returned by a previous action_requires_approval error.
`idem_key`	No	Optional key making a retry a no-op. Pass the same key when repeating an action you are unsure completed.

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 1, 2026

TDQS

A5/5.0

Behavior5/5

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

The description reveals the tool reads the current state before acting and does nothing if the value is already set, which is beyond the annotations. It also discloses the picker wheel's row-by-row behavior and that an option it does not contain fails by listing available options. This adds meaningful behavioral context not present in structured annotations.

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?

Every sentence earns its place: purpose, value syntax, picker failure behavior, preference over tapping, and exclusions for steppers/segmented controls. The description is a bit long but has zero filler and front-loads the most important usage guidance.

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

Completeness5/5

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

The description covers the tool's target elements, value formats, failure modes, and alternative tools. Since the schema already describes the four optional parameters and an output schema exists, the description supplies everything an agent needs to select and invoke the tool correctly.

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

Parameters5/5

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

Although the schema documents all five parameters, the description substantially enriches the meaning of the required `value` parameter with concrete input formats: 'on'/'off' for switches, percentage or fraction for sliders, and the exact picker spelling for wheels. This is crucial detail for correct invocation that the schema lacks.

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 opens with 'Set a switch, slider, or picker wheel to a value,' naming the specific verb and resource types. It further differentiates from ios_tap by explicitly stating that steppers and segmented controls should be tapped instead, so an agent can immediately know which tool handles which control type.

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

Usage Guidelines5/5

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

The description explicitly says 'Prefer this over tapping a switch' and explains why (state check prevents toggling off). It also names excluded control types (steppers, segmented controls) and instructs to tap their parts by label. This gives clear when-to-use and when-not-to-use guidance with alternatives.

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