ui_type

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

With no annotations, the description carries the behavioral burden and it does well by explaining that input is sent one character at a time with real key events and that this is slower. It also implies side effects like autocomplete/input mask reactions, though it doesn't mention return behavior or failure modes.

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 sentences, all front-loaded and purposeful: the core behavior, the key distinguishing trade-off, and a practical pointer for when to switch from ui_fill. No filler or repetition.

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 12 parameters and no output schema or annotations, the description is largely complete for selection and invocation: it explains what the tool does, when to choose it, and how it differs from the closest sibling. It could add more about return/error behavior, but that is not critical for the core use case.

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 input schema covers 100% of parameters, so the baseline is 3. The description does not add much about individual parameters, though the per-keystroke emphasis helps justify delay_ms indirectly.

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 action and resource: typing into a field one character at a time with real key events. It clearly differentiates from ui_fill by emphasizing per-keystroke behavior and gives concrete matching scenarios like search-as-you-type and input masks.

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?

It provides explicit when-to-use guidance: use it exactly when the field reacts per keystroke, and use ui_fill otherwise. It also names the alternative tool directly and covers the fallback case where ui_fill appears successful but the app doesn't register the input.

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