screen_scroll

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

With no annotations provided, the description carries the full burden. It discloses the direction convention and an environment variable requirement, which are useful behavioral details not present in the schema. However, it does not mention potential error behavior or whether scrolling targets the active element.

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 two short sentences, front-loaded with the action and prerequisite, and contains no unnecessary words. Every clause adds value.

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 tool with one parameter and no output schema, the description covers the core behavior, direction, and a key prerequisite. It lacks details on return values or failure modes, but these are likely not critical for a scroll action, and the given context is sufficient for invocation.

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 already covers the delta parameter with a description ('滚动格数（正=上，负=下）') that matches the tool description's direction info. Since schema coverage is 100%, the description adds no new parameter-level meaning beyond what is already present.

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 action as wheel scrolling ('滚轮滚动') with specific direction semantics (positive up, negative down). This distinguishes it from sibling tools like screen_click or screen_move, making the purpose unambiguous.

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 a clear prerequisite (VISION_ALLOW_SCREEN_CONTROL=1) that indicates when the tool is permitted to operate. It does not explicitly mention alternatives or exclusions, but the context is clear enough for a simple scroll action.

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