Double Tap Screen

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

Annotations already declare this is a non-readOnly, non-destructive, open-world interaction, so the safety profile is covered. The description adds the ref-vs-coordinate targeting distinction but discloses nothing further about effects (e.g. gestures that may zoom or trigger app behavior), rate limits, or permission needs. Adds marginal behavioral value over the annotations.

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?

Two tight sentences with the action and both targeting modes front-loaded, followed by the preference rule. No filler.

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 simple interaction tool with full annotations and 100% schema coverage, the description covers both invocation paths and the ref source. No output schema exists, but a tap returns no meaningful payload, so nothing important is missing; only explicit prerequisites (e.g. device enumeration) are left to the schema.

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 the baseline is 3. The description goes beyond the schema by naming the ref source ("from the latest mobile_list_elements_on_screen result") and giving the "@e5" format example, plus the preference rule, which helps the agent construct ref values correctly.

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?

States a specific verb+resource (double-tap on the screen) and spells out the two targeting modes. The action verb distinguishes it cleanly from siblings like mobile_click_on_screen_at_coordinates and mobile_long_press_on_screen_at_coordinates without needing to open their schemas.

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?

Provides an explicit selection rule between the two parameter modes: "Prefer ref when the element is listed." It does not explicitly route the agent away from single-click or long-press alternatives, but the action verb makes that implied. Clear context with no exclusions stated.

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