Screen Control

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motion_diff

Detect changes between two screen snapshots by identifying which tiles changed and their clickable centers. Use to verify an action had an effect or spot movement without OCR or vision.

Instructions

Text-only change detection between two snapshots: which tiles of the screen changed and their clickable centers. Use to verify an action had an effect or to spot movement without OCR/vision.

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": "motion_diff"
  }
}

Input Schema

Name	Required	Description	Default
`region`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 21, 2026

TDQS

A3.6/5.0

Behavior2/5

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

With no annotations, the description carries full behavioral burden. It mentions 'text-only' and 'without OCR/vision' but does not disclose how snapshots are obtained (e.g., whether it captures them internally), potential side effects, or performance implications. This ambiguity leaves the agent uncertain about the tool's execution model.

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 concise, front-loaded sentences pack the core purpose and usage into minimal space. No redundancy; every clause adds value.

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

Completeness3/5

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

The description covers the what and when but leaves a critical gap: the mechanism of 'two snapshots' is vague. Since the tool only accepts an optional region, it's unclear whether the agent must supply snapshots or if the tool manages them internally. The output schema exists, so return format is covered, but this ambiguity undermines completeness.

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

Parameters2/5

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

The schema description coverage is 0% and the description does not mention the 'region' parameter at all. The parameter is left completely unexplained, forcing the agent to guess whether it restricts detection to a screen area or serves another purpose.

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 clearly states the verb (detect), the resource (screen changes between two snapshots), and the output (changed tiles and clickable centers). It explicitly contrasts with OCR/vision, distinguishing it from sibling tools like ocr_screen.

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

Usage Guidelines4/5

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

Provides concrete use cases ('verify an action had an effect' or 'spot movement') and explicitly frames it as an alternative to OCR/vision. It doesn't name specific sibling tools, but the context is sufficient for an agent to decide when to use it.

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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