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

Annotations already establish that this is a non-read-only, non-idempotent, non-destructive, closed-world action, so the safety profile is covered. The description adds one useful trait beyond that ('Uses video coordinate space automatically'), but says nothing about effects on device state, scroll speed, or return behavior.

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?

Three short sentences with the action front-loaded. The final sentence 'No coordinate math needed' is largely redundant with the preceding coordinate-space claim, but the whole thing is efficiently sized.

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, well-annotated scroll action with a fully documented schema and no output schema, the description is adequate but thin. It omits any indication of when the action is complete, how it interacts with existing scroll position, or how it relates to swipe/scroll-to-element tools.

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 description coverage is 100%, so udid, amount (fraction 0.0-1.0, default 0.5), and the direction enum are fully documented in the schema. The description adds no meaning beyond that and never mentions the amount parameter, so the baseline 3 is appropriate.

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?

States a specific verb and resource ('Scroll the screen in a direction on an Android device'), clearly identifying the platform and action. It does not explicitly distinguish itself from close siblings like device_swipe, device_scroll_to_element, or device_gesture_path, so it falls short of a 5.

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 claim 'No coordinate math needed' hints at why one would pick this over device_swipe or device_gesture_path, but it never states when to use this tool versus those alternatives or any prerequisites. Usage is only implied.

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