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

With no annotations provided, the description must carry the full burden, and it does well: it discloses the direct input path, single-contact restriction, coordinate space ('iOS screen points'), and a specific failure mode ('Returns "no HID available" on iOS 17.x / no-tunnel'). It does not mention permissions or detailed success return behavior, but for a swipe operation this is substantial.

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 two sentences long, front-loaded with the primary action, and conveys the most important constraints and error condition without redundant detail. Every sentence earns its place.

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 tool's complexity (7 params, no output schema) and the broad sibling list, the description covers the essential context: no session needed, coordinate system, single-contact only, and a known iOS 17.x failure. It does not describe return values beyond the error string, but that omission is minor for a swipe action.

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?

The schema provides 100% parameter coverage, including descriptions for each x/y coordinate and the `norm` fraction semantics. The description adds the phrase 'Coordinates are iOS screen points', which reinforces but does not significantly extend the schema. Therefore, the baseline of 3 is appropriate.

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?

Description states the specific action ('Swipe from (x1,y1) to (x2,y2)') and the resource ('via the direct input path'), clearly distinguishing it from the sibling `ios_swipe` which would require an automation session. The verb and resource are unambiguous.

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 clearly indicates when this tool is appropriate ('no automation session needed') and provides a critical exclusion ('Returns "no HID available" on iOS 17.x / no-tunnel'). However, it does not explicitly name alternative tools like `ios_swipe` or `ios_drag_hid` for comparison, so it falls just short of full usage guidance.

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