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

Annotations already declare this as a safe, read-only, idempotent operation. The description adds a useful non-obvious fact about physical pixel coordinates and page_source bounds, but it does not describe what 'detailed info' includes beyond screen size or any other operational traits.

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, front-loaded with the primary purpose and followed by a tightly relevant coordinate note. Every sentence earns its place with no redundancy.

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 read-only tool with one fully documented parameter and rich annotations, the description gives enough context to call it correctly. It is slightly vague about exactly what 'detailed info' comprises, but the annotation coverage compensates.

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% for the single 'udid' parameter, so the schema already fully documents it. The description does not add any parameter-level meaning beyond what the schema provides, making the baseline 3 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 ('Get') and resource ('detailed info about a device'), and names a concrete return item ('physical screen size'). It does not explicitly differentiate from sibling tools like device_list or ios_device_info, so it is clear but lacks sibling routing.

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 coordinate note ('device_tap/device_swipe use PHYSICAL pixel coordinates... No scaling needed') implies a usage context for obtaining coordinate-related device metrics, but there is no explicit when-to-use or when-not-to-use guidance relative to alternatives.

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