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

Annotations declare readOnlyHint=false, idempotentHint=false, destructiveHint=false, but the description adds behavior the annotations do not: focus moves to the smallest focusable element under the point before Select is pressed, a point over non-focusable background is an error rather than a near miss, and select:false suppresses the click. Only missing detail is any return/confirmation behavior, which is minor here.

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?

Front-loads the scope ('Apple TV only') and the core action, then sequences prerequisite, error behavior, and alternatives. No sentence is filler; each carries a distinct constraint.

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 is needed for a fire-and-forget input tool, and the description covers prerequisites (read page source first), failure semantics (background = error), the non-clicking variant, and the name-based alternative. Nothing an agent needs to invoke this correctly is missing.

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 baseline is 3; however the description adds real meaning beyond the schema by explaining why select:false exists (to line up a long-press via ios_tv_button) and by reinforcing that x/y must come from page source rather than visual estimation. It adds context the schema's terse field descriptions do not.

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 (select) and resource (element at a screen coordinate) scoped to Apple TV, and explicitly distinguishes itself from the sibling tvos_focus ('For selecting by name instead of coordinate'). An agent can route correctly 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 explicit when-to-use and how: derive the coordinate from ios_page_source (cx,cy) or the [focused] flag, not from a screenshot; use select:false to move focus without clicking for a subsequent long-press; use tvos_focus for name-based selection. Conditions and alternatives are all named.

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