ui_select

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

With no annotations, the description carries the full behavioral burden and it delivers: it discloses that custom dropdowns are opened and the matching option clicked, and that the tool reports visible options when nothing matches. This is actionable context beyond the schema, though it does not describe waiting behavior or side effects in detail.

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 three sentences with no filler: primary action, native-vs-custom handling, and no-match reporting. It is front-loaded and every sentence contributes behavior an agent needs.

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 description covers the core action, the key implementation nuance, and the failure-report behavior, which partially substitutes for the missing output schema. With 10 parameters but full schema coverage, nothing essential to invoking correctly is missing, though more detail on return values or side effects would make it fully 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 description coverage is 100%, so the schema already documents all 10 parameters including option, by, exact, and timeout_ms. The description adds useful context about matching by visible label or value and the custom-dropdown click path, but it does not add substantial meaning beyond what the parameter descriptions already provide.

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 domain: 'Choose an option in a dropdown, by visible label or by value.' It also distinguishes this tool from generic clicks by explicitly covering native <select> elements and the custom div-based dropdowns most applications use. This makes the tool's purpose clear and separable from siblings like ui_click.

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 frames when to use the tool: whenever a dropdown selection is needed, and it explains how native vs custom dropdowns are handled. It does not explicitly name sibling alternatives or state when not to use it, so it stops short of full exclusion guidance.

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