MCP Scrcpy Vision

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

With no annotations provided, the description carries full burden but only partially discloses behavior. It states the return format ('Returns image/png') but lacks critical details like whether this requires device permissions, if it works on locked screens, potential rate limits, or error conditions. For a tool that interacts with hardware, this is a significant gap.

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?

Extremely concise and front-loaded with all three sentences earning their place: first states the core functionality, second clarifies implementation advantages, third specifies return format. Zero wasted words.

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?

For a tool with no annotations, no output schema, and 0% schema coverage, the description is minimally adequate. It covers purpose, implementation distinction, and return format, but lacks behavioral details (permissions, errors) and parameter explanations that would make it complete for safe agent use.

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 has 0% description coverage for its single parameter 'serial', but the description doesn't explicitly explain what 'serial' means. However, given there's only one parameter and the tool's purpose is clear from context (device screenshot), the description adequately compensates by implying device identification is needed. A perfect score is withheld since parameter meaning isn't directly addressed.

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 ('Take a snapshot screenshot'), resource ('from a device'), format ('PNG'), and implementation method ('Uses adb exec-out screencap -p'), distinguishing it from sibling tools like android.vision.startStream (streaming) or android.ui.dump (UI hierarchy).

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 by mentioning it 'Works without scrcpy/ffmpeg', which implies when to use this simpler method versus alternatives requiring those dependencies. However, it doesn't explicitly state when NOT to use it or name specific alternative tools.

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