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

With no annotations provided, the description carries the full burden, and it delivers: it reveals the return content (attributes, bounds, centre, ranked locators), the ordering logic (smallest-first), coordinate semantics (iOS screen points, same space as ios_tap), an edge case (zero-area elements kept), and the session prerequisite. This is exceptionally transparent for a read-only tool.

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?

Four sentences, each carrying distinct information: core behavior, return format/order, usage context, and the zero-area edge case plus prerequisite. It is appropriately front-loaded and not redundant, though slightly dense. It could be trimmed slightly but remains efficient.

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?

No output schema exists, so the description compensates by specifying the exact return fields, ordering, coordinate space, and an important edge case. It also states the session requirement informatically. An agent gains everything needed to invoke this tool correctly with no gaps.

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 the baseline is 3. The description adds only a restatement of the coordinate system ('iOS screen POINTS, same space as ios_tap') which is already conveyed by the schema's 'screen points' mention. No additional parameter-specific meaning is provided beyond the schema.

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 opens with a specific verb and resource: 'List addressable elements whose bounding box INTERSECTS the given rectangle.' It also names its sibling counterpart (device_elements_in_region), immediately distinguishing it from the generic device-level tool. This is a precise, unambiguous purpose statement.

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?

It explicitly says when to use it: 'Use to enumerate a region (tab bar, dialog, list section) without reading the whole tree.' It also mentions being the counterpart of device_elements_in_region, which serves as a clear alternative, and implies when not to use (avoid whole-tree reads). This leaves no ambiguity about selection.

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