Type Text

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

Annotations mark readOnlyHint=false (a mutating operation), openWorldHint=true, and destructiveHint=false. The description adds only the 'focused element' precondition, which is mild useful context, but it does not disclose what happens on submit=true (side effects of submission), whether text replaces or appends existing content, or whether the device must be foregrounded. Since the annotations do not carry a safety profile that the description can lean on, more behavioral disclosure would be expected. No contradiction with 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?

A single sentence, front-loaded, with zero filler. It gets the core purpose across efficiently. Slightly under-specified rather than overly verbose, but for a simple tool whose parameters are fully covered by the schema, this length is appropriate.

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 is relatively simple with 3 fully documented parameters and no output schema, so the burden is modest. The description conveys the core purpose and the focused-element precondition. However, it omits usage context (when to choose typing over button-press or tap), which an agent would need to select it correctly among the large sibling set. Adequate for basic invocation but with a clear guidance gap.

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%, so the schema fully documents all three parameters (text, device, submit), including the device hint to consult mobile_list_available_devices. The description adds nothing beyond the schema for parameters, so the baseline of 3 applies. The description's 'focused element' wording loosely relates to the text target but does not clarify the device or submit semantics beyond what the schema already states.

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 and resource: 'Type text into the focused element.' This clearly identifies the action and target, and it distinguishes the tool from siblings like mobile_click_on_screen_at_coordinates, mobile_press_button, and mobile_swipe_on_screen, which perform different input actions. It is not a pure tautology of the title, since 'focused element' adds meaningful targeting context.

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?

There is no guidance on when to use this tool versus alternatives. The description implies usage for entering text but never states prerequisites (e.g., the target element must first be focused, possibly via a click or tap tool), nor does it mention exclusions or route the agent toward sibling tools. An agent is left to infer when typing is the right action versus pressing a button or tapping coordinates.

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