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

With no annotations, the description carries the transparency burden. It clearly discloses that the tool sets the select value, dispatches input and change events, and is React/controlled-safe. It also states error behavior (throws for non-select or no matching option) and auto-detection of browser type, giving the agent a solid understanding of side effects and 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?

The description is concise and well-structured, with the core action front-loaded. Each sentence adds essential information: purpose, matching criteria, side effects, and error conditions. There is no redundancy or irrelevant detail, achieving high information density.

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 adequately covers the operation, matching criteria, side effects, and errors, but lacks information about the return value or confirmation of success. Since there is no output schema and no annotations, this gap leaves the agent uncertain about what to expect after invocation. Essential preconditions like element visibility or page state are also omitted, making the description sufficient but not 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?

The schema already covers all parameter descriptions (100% coverage), so the baseline is 3. The description adds meaningful semantics beyond the schema by specifying that exactly one of value/label/index must be provided, which is a crucial constraint not stated in the individual parameter descriptions. This enhances the agent's ability to construct valid inputs.

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 clearly states the tool's function: choosing an option in a <select> dropdown on a mobile browser page. It specifies the input methods (CSS selector or ref) and matching criteria (value, label, or index), distinguishing it from generic click/type tools. The scope (iOS Safari or Android Chrome) is also explicit.

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 implies the tool is for selecting dropdown options but does not explicitly state when to use it over alternatives like webpage_click or session_execute. It mentions throwing if the target is not a <select>, which hints at its specific purpose, but there is no direct guidance on when to choose this tool or when to avoid it.

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