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 and does so effectively by disclosing key behavioral traits: it describes performance differences (instant vs. slower), encoding issues (spaces as %s), and dependency on stream state. However, it does not cover aspects like error handling or permissions, leaving some gaps.

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 front-loaded with the core purpose ('Types text') and efficiently explains the behavioral context in one sentence. Every part adds value, with no wasted words, making it highly concise and well-structured for quick understanding.

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 (a tool with two parameters, no annotations, and no output schema), the description is somewhat complete by covering behavior and usage context. However, it lacks details on parameter semantics, error cases, or return values, which are important for full understanding in this context.

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, but it does not explicitly explain the parameters (serial and text). It implies 'text' is the input to type and 'serial' relates to the device, but no details on formats or constraints are provided. This adds minimal value beyond the schema's basic structure.

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 ('Types text') and resource ('on the device'), distinguishing it from sibling tools like android.input.keyevent (for key events) or android.input.tap (for taps). It precisely defines the tool's function without being vague or tautological.

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 on when to use it by explaining the fallback mechanism (fast scrcpy when stream active, slower adb otherwise), but it does not explicitly state when not to use it or name alternatives among siblings (e.g., android.input.keyevent for non-text input). This gives good guidance but lacks explicit exclusions.

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