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

With no annotations, the description carries the full burden. It discloses the active session requirement and auto-start behavior, states that it scrolls until visible, and returns coordinates. It does not cover failure scenarios (e.g., element not found) but provides solid context for a non-destructive scroll operation.

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?

Two sentences deliver the action, the benefit, and the requirement with no fluff. The primary action is front-loaded, and every phrase adds value. It is an exemplary concise definition.

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 3-parameter tool with no output schema, the description covers purpose, session requirement, and outcome. It lacks explicit failure/timeout behavior, but that is a minor gap. Overall, it is sufficiently complete for an agent to invoke correctly.

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 parameters are fully described. The description adds contextual meaning by linking the label to the scroll target and noting the coordinate return, which reinforces the purpose. However, it does not add significant new parameter details beyond the schema, so a baseline of 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?

The description clearly states a specific verb (scroll), a resource (screen), and an outcome (element visible and coordinates returned). It also mentions the benefit of eliminating multi-swipe guesswork, and the iOS-specific session requirement distinguishes it from generic alternatives. The purpose is unambiguous and well-defined.

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 implies usage for locating off-screen elements by label ('Eliminates multi-swipe guesswork'), but it does not explicitly contrast with sibling tools like ios_swipe or device_scroll_to_element. It mentions the session prerequisite but offers no exclusions or alternative selection criteria, leaving the when-not-to-use case unstated.

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