phone_home_layout

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

Goes well beyond the annotations: apply/restore replace the whole layout, the replaced layout is backed up first, and SpringBoard may reintroduce App Library apps across several passes so a re-read is required after writing. Also discloses that an unreadable device errors rather than returning an empty screen. The read/write split is consistent with readOnlyHint=false and destructiveHint=true; a 5 is withheld only because eventual-consistency timing and partial-failure reporting on apply are not pinned down.

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-loaded correctly with the read purpose and page-index caveat, but it is a single dense paragraph that folds the read contract, coordinate semantics, device prerequisites, and four write actions into one block with no separation between read and write modes. Every sentence carries information, yet the structure forces re-parsing to find the write rules.

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 five-parameter tool with no output schema and a destructive write path, the description covers prerequisites (usbmuxd, no Runner needed), failure behavior (error not empty result), output-field semantics (positions_complete, null positions), write ordering and confirmation, and undo. An agent has enough to invoke both the read and the write modes correctly without guessing.

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?

Adds meaning the schema cannot: page indexes are persisted icon state including hidden and Focus-filtered pages, not the visible page-control indexes, and row/col values are derived from icon-state order and grid metrics with null or positions_complete=false meaning unknown rather than safe. Also clarifies file is a plist on the Mac produced by a backup and that confirm is a human-agreement gate, so the write contract is unambiguous.

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?

Opens with a specific verb and resource set: 'Read all home-screen pages, Dock, folder pages and widget stacks from the paired iPhone', and explicitly separates itself from screenshot/tap siblings ('without opening folders, swiping, or taking screenshots'). The tool is really two modes (read plus backup/preview/apply/restore) bundled under one name, so an agent must read the whole paragraph to learn the tool also mutates, which keeps it short of a 5.

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 when-not-to-use conditions: no drivable=true or XCTest Runner needed, and 'never reconnect or open Home solely for this read'. For the write path it names the required sequence (backup or preview first, then apply/restore only with confirm=true after the person agreed to the preview) and the recovery path ('Undo with action=restore'). Alternatives are named rather than implied.

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