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appium_screenshot

Capture a mobile app screenshot and save it as a PNG. Optionally target a specific element by its UUID to capture only that component.

Instructions

Take a screenshot and save as PNG. Optionally provide elementUUID to capture only that element.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
maxWidthNoResize to at most this width in pixels, preserving aspect ratio.
sessionIdNoSession ID; defaults to the active session.
elementUUIDNoCapture this element; omit for the full screen.
returnRawBase64NoReturn inline PNG instead of saving, for explicit manual use when the server file is inaccessible. LLMs must keep false and use the saved path.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed4 schema fields changedv1.95.0
    • changedInput schema / properties / elementUUID / description
      Previous value: -"Optional element UUID. If provided, captures only this element. If omitted, captures full screen."New value: +"Capture this element; omit for the full screen."
    • changedInput schema / properties / maxWidth / description
      Previous value: -"Optional maximum width in pixels to resize the screenshot. The aspect ratio is preserved. Useful for reducing token usage when sending screenshots to LLMs."New value: +"Resize to at most this width in pixels, preserving aspect ratio."
    • changedInput schema / properties / returnRawBase64 / description
      Previous value: -"When true, returns the raw base64-encoded PNG image instead of saving it to disk. This should only be enabled when a human explicitly invokes the tool manually, typically to view the screenshot on a different machine (e.g. when the server runs on a remote machine and the saved file is not accessible). An LLM must always keep this false and rely on the saved file path."New value: +"Return inline PNG instead of saving, for explicit manual use when the server file is inaccessible. LLMs must keep false and use the saved path."
    • changedInput schema / properties / sessionId / description
      Previous value: -"Session ID to target. If omitted, uses the active session."New value: +"Session ID; defaults to the active session."
  2. First observedv1.92.11

TDQS

A3.8/5.0
Behavior3/5

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

The description discloses the core behavior: capturing a screenshot and saving it as PNG. It does not contradict the annotations, but with readOnlyHint false and openWorldHint false, the annotations add little context, and the description does not mention output paths, return semantics, or limitations such as element visibility.

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 one concise sentence that front-loads the main action and then introduces the optional element capture. Every word contributes to understanding, with no filler or repetition.

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 simple screenshot tool with fully documented parameters, the description plus schema is largely sufficient. It lacks an explicit statement of the return value, such as the saved file path, but the returnRawBase64 parameter description partially covers that expectation.

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 all parameters are already well documented. The description mostly restates the elementUUID behavior found in the schema without adding significant new meaning, so the baseline of 3 is appropriate.

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 uses a specific verb and resource: 'Take a screenshot and save as PNG.' It also distinguishes the element-capture mode from full-screen capture, making the tool's purpose clear and distinct from siblings like appium_screen_recording or appium_get_page_source.

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 purpose implies the tool should be used for still visual capture, and the optional elementUUID note adds a usage mode. However, it does not explicitly mention alternatives, such as screen recording or page source, or state when one should be preferred over the other.

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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