screen_capture

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

No annotations are provided, so the description must carry the full burden. It states the tool captures the screen and returns a PNG, but does not disclose any behavioral traits such as whether it is read-only, required permissions, or potential side effects. For a simple capture tool, this is minimal but insufficient for full transparency.

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 only two sentences, both front-loaded with the core action and return type. Every word is informative and there is no redundancy. It is 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 no parameters and no output schema, the description is mostly complete for a simple screen capture tool. It covers purpose, output, and use case. However, it could be slightly more detailed (e.g., whether it captures full screen or active window, or any limitations). Overall, it meets minimum viability but leaves minor gaps.

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 input schema has zero parameters, so no parameter information is needed from the description. The description does not add parameter details, but that is acceptable because none exist. According to guidelines, baseline is 4 with 0 params, and the description adds context about the tool's function.

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 action (截取屏幕, capture screen), the resource (设备当前屏幕, device current screen), and the output (返回 PNG 图片, returns PNG image). It also mentions the use case (查看设备当前界面状态, view current interface state). This effectively distinguishes it from sibling tools like dump_ui_tree or observe_device.

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 includes the purpose '用于查看设备当前界面状态' (used to view current interface state), which implies when to use it. However, it does not explicitly state when not to use it or provide alternatives among the many sibling tools. Some guidance is present but not comprehensive.

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