获取 DOM 样式快照

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

无注解，描述承担了行为披露责任。说明这是纯文本操作、无需授权，只输出可见节点，且穿 shadow DOM，这补充了安全性和执行行为。虽然未讨论 maxNodes/depth 截断或返回失败情况，但关键行为已明确。

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?

两句话紧凑完成功能说明、输出内容说明、适用场景和替代工具路由，信息密度高且无冗余。关键行为前置，替代方案收尾，结构清晰。

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?

无输出 schema，描述说明了输出内容（每行几何、样式、文本），无注解时也覆盖了授权和只读性。5 个参数中必需项在 schema 中已有定义，整体对调用该工具所需上下文已足够；仅缺少对截断或 selector 无效时的行为说明。

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?

Schema 描述覆盖率为 100%，参数本身在 schema 中已有完整说明。描述没有额外深化参数语义，但也不构成负担，按 baseline 3 评分合理。

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?

描述明确说明对指定元素子树生成「虚拟截图」，包含几何、样式、文本和 shadow DOM 穿透，动词和资源具体。与 get_screenshot 的差异通过「需要真实渲染像素时再用 get_screenshot」直接点出，能清晰区别于兄弟工具。

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?

描述明确给出使用场景：验证颜色、布局、定位的首选；并明确列出何时应改用 get_screenshot（canvas 内容、图片、遮挡观感）。提供了 when-to-use 和 when-not-to-use 的清晰指引。

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