get_layout_metrics

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

With no annotations, the description must carry the burden of behavioral disclosure. It clearly implies a read-only operation via 'get' and specifies the returned properties, but it does not explicitly state that it has no side effects or what the units are. The property list adds transparency, but more context (e.g., content size meaning the scrollable document area) would be better.

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?

A single sentence that is front-loaded with the verb and resource, and the parenthetical list of properties adds specificity without padding. No 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 simple getter with no output schema, the description is largely sufficient. It names all required return fields (viewportWidth/viewportHeight/contentWidth/contentHeight). However, it does not clarify the semantics of 'content size' (e.g., whether it refers to the full scrollable area), which could cause ambiguity for an AI agent.

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 tool has zero parameters, so the schema is trivial. The description provides relevant context by naming the returned metrics, which indirectly explains why no input is needed. Baseline for 0 params is 4, and this description meets that baseline.

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 uses a specific verb (获取/get) with a clear resource (页面视口尺寸和内容尺寸/page viewport and content size) and even lists the exact property names. This distinguishes it from sibling tools like get_box_model or get_computed_styles, which focus on element-specific metrics.

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?

No guidance is provided on when to use this tool versus alternatives, such as get_box_model for element dimensions or get_dom_tree for overall structure. The description implies its use for page-level metrics but does not state exclusions or conditions.

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