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

With no annotations, the description fully discloses behavior: the hold at both ends, how holdStartMs and holdEndMs affect app interaction, the failure mode of a bare swipe, single-contact limitation, and the 'no HID available' error on iOS 17.x/no-tunnel. This is rich, non-obvious behavioral context.

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 information-dense. Each sentence serves a purpose: defining the action, contrasting with a sibling, listing use cases, explaining coordinate normalization, and stating constraints/error behavior. No wasted words.

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?

Given the complexity (8 params, nested objects, no output schema), the description covers the operation thoroughly: mechanics, timing, coordinate systems, limitations, and known error conditions. It provides enough context for correct invocation without needing additional documentation.

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 baseline is 3. The description adds meaning beyond schema by explaining norm=true with the formula 'pixelInScreenshot ÷ screenshotSize' and its benefits (scale-free, matches frontend), and by clarifying the purpose of holdStartMs/holdEndMs in behavioral terms. Not every parameter is described (udid, durationMs), but the key ones gain context.

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 clearly states a specific action (drag-and-drop with press-and-hold, move, release) on a specific resource (direct input path). It explicitly distinguishes itself from sibling ios_swipe_hid by emphasizing the hold at both ends, which differentiates it from a simple swipe.

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 description provides explicit use cases ('reordering, sliders, and canvas drag-and-drop') and contrasts with ios_swipe_hid, explaining when a bare swipe fails. It also notes 'no automation session needed' and 'Single-contact only,' giving clear guidance on when to use this tool versus alternatives.

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