previewapk_hierarchy

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

With no annotations, the description carries the burden and does disclose the key behavioral trait: this returns a structured tree rather than pixels and is 'much faster and cheaper' than a screenshot. It does not state that the operation is non-mutating, nor any error/default behavior, but the cost model and return nature are substantive context beyond a bare purpose statement.

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 tightly packed sentences with zero waste: the resource and return shape come first, the performance rationale second, and the alternative routing last. Nothing is redundant or filler.

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?

There is no output schema, so the description correctly takes on the job of enumerating return fields, which it does thoroughly. The only meaningful hole is the unexplained 'device' parameter, which is the sole input.

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 0% and there is one parameter ('device') that is never mentioned or explained in the description. The description must compensate for the coverage gap and does not, so the agent gets no guidance on what device identifier to supply or what the default is.

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?

Names a specific verb and resource ('Get the current screen as a UI element tree') and enumerates the returned fields (class, text, content-desc, resource id, bounds, center coordinates, state flags). It explicitly contrasts itself with previewapk_screenshot ('instead of pixels'), so an agent can tell the two apart without opening a schema.

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?

Gives explicit when-to-use conditions ('find elements, read values, check state' for navigation and assertions) and names the alternative with its own use case ('Use previewapk_screenshot for visual checks (layout, overlap, images)'). The routing decision is fully specified.

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