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

With no annotations provided, the description carries the full burden. It discloses the multi-phase gesture mechanics (hold, then motion), default timings, the coordinate space (physical pixels from page_source bounds), and the deliberate-grab requirement. It does not explicitly state that a drag is a mutating/screen-changing operation or mention any permission/auth needs, but the gesture mechanics disclosure is substantive and useful.

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?

Three tight sentences deliver purpose, differentiation, use cases, and coordinate semantics with zero filler. Every sentence earns its place, and the most critical selection-differentiation detail (how it differs from swipe/long_press) is front-loaded.

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?

The tool has 7 params (5 required) with 100% schema coverage and no output schema (returns void presumably). The description covers the gesture mechanics, defaults, coordinate space, alternatives, and use cases. The only gaps are edge-case behavior (e.g., zero durations, out-of-bounds coords) and whether the drag can cross screen boundaries, but for a gesture tool with full schema coverage this is largely 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 coverage is 100%, so baseline is 3. The description adds value by explaining the semantic roles of the coordinate parameters within the gesture flow: (x1,y1) is the hold point for the deliberate grab, and (x2,y2) is where the drag ends. It also explains the role of holdMs (grab) and durationMs (motion). However, it does not detail edge cases like what happens if holdMs is 0 or coordinate bounds.

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 uses a specific verb+resource ('Drag-and-drop on an Android device') and clearly details the mechanism (hold at (x1,y1), move to (x2,y2) over duration). It explicitly distinguishes itself from sibling tools device_swipe (no hold) and device_long_press (no motion), providing concrete if/then decision criteria.

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 explicitly names alternative tools and when NOT to use them ('Distinct from device_swipe... and device_long_press...'). It gives concrete use cases ('app-icon reorder, drag-into-folder, slide gestures that need a deliberate grab') that map to when this tool is appropriate, which is strong guidance for selection.

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