adb-ai

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adb_screenshot

Captures an Android device screen as an image for inspection, optionally scaling large screens or returning the original size via max_size.

Instructions

Capture the screen and return it as an image you can look at. Large screens are scaled down on the way (ffmpeg, when it is installed) so you get the picture sooner; pass max_size to change that, or 0 for the untouched original.

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": "adb_screenshot"
  }
}

Input Schema

Name	Required	Description	Default
`device`	No	serial, ip[:port] or saved alias; omit to use the default device
`max_size`	No	longest side in pixels, default 1280; 0 sends the full-size PNG

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 27, 2026

TDQS

A3.8/5.0

Behavior4/5

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

With no annotations, the description carries the behavioral burden and does well: it discloses that large screens are scaled down, that ffmpeg is used when installed, and that max_size controls scaling with 0 meaning original. It does not cover error behavior or latency, but for a read-only capture operation the key behavioral traits are present.

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?

Two compact sentences with zero waste. The primary purpose is stated first, followed by the scaling caveat and parameter pointer. Nothing is buried or redundant.

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 two-parameter, fully optional screenshot tool with no output schema, the description is nearly complete: it says what is returned (an image) and how scaling works. Missing are only minor details like output format specifics and behavior when no device is available, which the schema partially covers via the device parameter.

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 already explains both device and max_size in detail. The description reinforces max_size semantics ('pass max_size to change that, or 0 for the untouched original') but adds no information beyond what the schema provides. Baseline 3 is appropriate.

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 specific verb and resource: 'Capture the screen and return it as an image you can look at.' An agent immediately knows this is a screenshot tool. It does not differentiate itself from sibling adb_mirror, which may also show the screen, so sibling distinction 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 Guidelines3/5

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

The description implies usage ('an image you can look at') but gives no explicit when-to-use, when-not-to-use, or alternatives. An agent can infer this is for visual inspection, but must decide on its own versus adb_mirror or other screen-related tools.

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