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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description layers on real behavioral detail: INTERSECTS semantics, smallest-first sort so the most specific element returns first, zero-area elements retained because iOS tab-bar labels report 0x0, and the requirement for an active iOS automation session.

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?

Dense but front-loaded: the core operation comes first, then the ordering guarantee, the zero-area caveat, the coordinate-space note, and the session prerequisite. Every sentence carries information, though it runs long enough that it is not maximally tight.

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?

With 6 parameters, no output schema, and a read-only annotation set, the description compensates fully by describing the returned fields (attributes, bounds, centre, ranked locators), the sort order, and the session prerequisite. An agent has everything needed to call and interpret it.

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 the coordinates, udid, and limit are already documented in the schema. The description adds the useful clarification that coordinates are iOS screen POINTS, the same space as ios_tap, but says nothing extra about limit or ordering interactions with the cap. Baseline 3 applies when the schema does the work.

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 (list) plus resource (addressable elements intersecting a rectangle) and scope (bounding-box intersection, not containment). It also explicitly names itself as the counterpart of device_elements_in_region, so an agent can place it against the platform sibling without opening either 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 a clear use case (enumerate a tab bar, dialog, or list section without reading the whole tree) and contrasts with device_elements_in_region. It lacks explicit when-not guidance relative to ios_page_source or ios_find_element, so it falls short of a full 5.

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