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

With no annotations, the description must carry the behavioral burden. It adds one useful behavioral detail—each count scrolls approximately one screen—but does not mention whether scrolling is instantaneous, waits for rendering, or handles page boundaries. Nevertheless, scrolling is a low-risk, non-destructive operation and the core behavior is clear.

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 extremely concise—one short sentence plus inline parameter hints—and front-loads the main action before parameter details. There is no filler or repetition.

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 two-parameter tool with no output schema, the description plus schema cover the essential information: what to scroll, which direction, how many times, and the scroll amount. It could be more complete by stating when to use it relative to siblings, but nothing critical is missing for a basic call.

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 coverage is 100%, so it already documents the direction enum and count default. The description adds meaningful semantic context by defining count as approximately one screen per scroll, clarifying the effect of changing count beyond the schema text.

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 identifies the tool as page scrolling with direction and count parameters. It is distinct from sibling tools (click, navigate, screenshot, snapshot) even though it does not name an alternative explicitly. The verb+resource pair ('页面滚动') is specific, but sibling differentiation is left implicit.

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 intended use is implied by the name and description: whenever the agent needs to scroll the page. However, there is no explicit 'when to use' guidance, no exclusions, and no reference to alternatives such as bf_navigate for moving to a new page.

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