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

No annotations are provided, so the description carries the burden of behavioral disclosure. It explains the mechanism (move focus ring, press Select), the failure model (error on non-focusable background, not a near miss), and the effect of select:false. It does not mention side effects like whether pressing Select triggers navigation or what happens if multiple elements overlap, but for a focused UI automation tool this is sufficient. Lacks a note on required permissions or if the device must be paired, but that's minor.

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?

The description is compact yet dense: three sentences front-load the core action and key constraint, then add usage nuance and an alternative. Every sentence carries information – no filler, no repetition of schema property names. Highly 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?

For a 4-parameter tool with no output schema and no annotations, the description is thorough: it explains how to obtain inputs, what action is taken, the select:false behavior, and the alternative tool. It does not describe the return value or outcome (e.g., success/failure signals), but given simplicity it's nearly complete. Could mention pairing requirements or error codes, but those are arguably covered by the error-near-miss note.

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 value by explaining how x and y should be derived (from ios_page_source centre) and clarifying the select parameter's default and purpose. It also emphasizes the error condition related to coordinates, which semantically reinforces the schema docs.

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 clear platform constraint ('Apple TV only') and a specific verb+resource: 'Select the element at a screen coordinate: move the focus ring ... and press the remote Select.' It precisely defines what the tool does, distinguishes it from tvos_focus (selecting by name), and mentions the select:false variant. This is far beyond a tautology.

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 gives explicit when-to-use guidance: use coordinates from ios_page_source, never eyeball from screenshots, and states that clicking non-focusable background is an error. It also names the alternative for name-based selection (tvos_focus) and explains when to use select:false for setting up a long-press. This is model guidance.

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