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Mobile Next MCP Server

Official
by mobile-next
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TypeScript
Hybrid

Take Screenshot

mobile_take_screenshot
Read-only

Capture a live screenshot from an identified mobile device to inspect current screen contents and map visible positions back to device coordinates for accurate taps.

Instructions

Take a screenshot of the mobile device. Use this to understand what's on screen, if you need to press an element that is available through view hierarchy then you must list elements on screen instead. The screenshot is usually smaller than the screen, so when the device reports its screen size the result also states how to convert positions in the screenshot into screen coordinates before tapping. Do not cache this result.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
scaleNoScale factor (0.0-1.0). Ignored if maxSize is provided.
deviceYesThe device identifier to use. Use mobile_list_available_devices to find which devices are available to you.
maxSizeNoMaximum width/height in pixels, keeping aspect ratio. Defaults to 1024.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv1.0.6
    • changedInput schema / $schema
      Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"
  2. Changed2 schema fields changedv1.0.3
    • addedInput schema / properties / maxSize
      Added value: +{
+  "description": "Maximum width/height in pixels, keeping aspect ratio. Defaults to 1024.",
+  "exclusiveMinimum": 0,
+  "maximum": 9007199254740991,
+  "type": "integer"
+}
    • addedInput schema / properties / scale
      Added value: +{
+  "description": "Scale factor (0.0-1.0). Ignored if maxSize is provided.",
+  "exclusiveMinimum": 0,
+  "maximum": 1,
+  "type": "number"
+}
  3. Changed4 schema fields changedv1.0.0
    • removedInput schema / additionalProperties
      Removed value: -false
    • addedInput schema / properties / device
      Added value: +{
+  "description": "The device identifier to use. Use mobile_list_available_devices to find which devices are available to you.",
+  "type": "string"
+}
    • removedInput schema / properties / noParams
      Removed value: -{
-  "additionalProperties": false,
-  "properties": {},
-  "type": "object"
-}
    • changedInput schema / required
      Previous value: -[
-  "noParams"
-]New value: +[
+  "device"
+]
  4. First observed

TDQS

A4.1/5.0
Behavior4/5

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

Annotations already declare readOnlyHint and openWorldHint, so the bar is lower, yet the description still adds real behavioral context the annotations cannot convey: the image is usually smaller than the screen, the result states how to convert screenshot positions into screen coordinates before tapping, and the result must not be cached. It stops short of noting anything about size/quality tradeoffs (scale, maxSize) affecting the returned image.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, zero filler, and the primary purpose is front-loaded before the alternative-tool guidance and the coordinate-conversion caveat. Slightly dense in the middle sentence but every clause carries usable information.

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?

With no output schema, the description compensates by explaining that the result includes coordinate conversion metadata, which is the key thing an agent must know to act on the returned image. Nothing critical is missing for a read-only capture tool, though the interaction with mobile_save_screenshot remains unaddressed.

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 parameters are already fully self-documented by the schema (device, scale, maxSize with ranges and defaults). The description adds nothing about how scale or maxSize change the output, so the baseline 3 applies rather than anything higher.

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?

States a concrete verb+resource ("Take a screenshot of the mobile device") and explicitly names the condition that routes the agent elsewhere (view hierarchy -> list elements). It distinguishes itself from mobile_list_elements_on_screen but never clarifies its relationship to the sibling mobile_save_screenshot, so the boundary between capture-and-return vs capture-and-persist is left implicit.

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?

Gives an explicit when-to-use ("understand what's on screen") and an explicit when-not-to-use with the named alternative ("if you need to press an element that is available through view hierarchy then you must list elements on screen instead"). This is exactly the routing an agent needs between the two screen-inspection tools.

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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