pinch

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

No annotations are provided, so the description carries the full behavioral burden. It does not disclose gesture duration, whether the call blocks until the gesture completes, how velocity interacts with the gesture, or any failure/retry behavior, leaving the agent with only the bare action semantics.

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?

A single front-loaded sentence with the action verb first and zero filler. It is efficient, though there is so little content that nothing beyond the core action is anchored for the reader.

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?

An output schema exists, so return values need not be described, and all five parameters are documented in the schema. However, for an unannotated device-interaction tool with a timing-sensitive velocity parameter, the description omits any gesture-timing or completion behavior, leaving it only minimally complete.

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% and the schema already explains x/y as the pinch center, scale as the zoom direction, velocity as scale-per-second, and device_id as the simulator UDID. The description adds nothing beyond 'at coordinates' mapping loosely to x/y, so baseline 3 applies.

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 states a specific verb ('Perform a pinch gesture') and the resource/effect (zoom in/out) plus where it happens (at coordinates), which is unambiguous against siblings like tap, swipe, double_tap, and long_press. It stops short of explicitly differentiating from those siblings, so a 4 rather than 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?

The parenthetical '(zoom in/out)' implies the intent of the gesture, but there is no guidance on when to choose pinch over swipe, double_tap, or other gestures, nor any preconditions. Like the update_drive calibration case, this lacks any when-to-use or alternative routing.

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