MCP Scrcpy Vision

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It adds useful context about the underlying implementation (adb shell input draganddrop) and version-dependent fallback behavior, which helps the agent understand execution characteristics. However, it doesn't mention potential side effects, error conditions, or what happens if the gesture fails, leaving some behavioral aspects unclear.

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

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

The description is perfectly concise with two sentences that each earn their place. The first sentence states the core functionality, and the second provides important implementation details. No wasted words, and the information is front-loaded with the primary action.

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

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

Given the complexity of a device interaction tool with 6 parameters, no annotations, and no output schema, the description provides adequate but incomplete context. It covers the core action and implementation details but lacks information about return values, error handling, and full parameter explanations. For a tool that performs device input gestures, more behavioral context would be helpful.

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

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

The schema description coverage is 0%, so the description must compensate for all 6 parameters. While it mentions 'start coordinates' and 'end coordinates' which map to startX/startY and endX/endY, it doesn't explain the 'serial' parameter (device identifier), 'durationMs', or provide any formatting details for coordinates. The description adds minimal semantic value beyond what's obvious from parameter names.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('drags from start coordinates to end coordinates'), identifies the resource (Android device via coordinates), and distinguishes it from siblings like 'android.input.swipe' by mentioning the fallback mechanism. It uses precise technical terminology that differentiates this drag-and-drop gesture from other input methods.

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

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

The description provides clear context about when to use this tool by specifying it works on Android 7+ with a fallback to swipe on older versions. However, it doesn't explicitly state when NOT to use it or name specific alternatives among siblings, though the fallback mention implies 'android.input.swipe' as an alternative for older versions.

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