browser_fill

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

With no annotations provided, the description carries full responsibility for disclosing behavioral aspects. It states the effect (fill) but does not mention whether this triggers events, replaces existing content, or handles missing selectors. It lacks any safety or side-effect information, which is significant for a mutation operation.

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 a single sentence that is front-loaded with the verb and resource. Every word contributes to understanding, with no unnecessary 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?

The tool is relatively simple with only two string parameters, and the description covers the core behavior. However, given no annotations and no output schema, it leaves out behavioral context such as return values, error handling, or event triggering, making it only moderately complete for an agent.

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 0%, requiring the description to explain parameters. The description clarifies that 'selector' is a CSS selector and 'value' is the value to fill, adding meaning beyond bare parameter names. However, it does not provide additional details like value format or selector syntax nuances.

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 action ('Fill') and the target resource ('input/textarea identified by a CSS selector'), making the tool's purpose unambiguous. It does not explicitly differentiate from sibling tools like browser_type, but the verb 'fill' and target element type provide reasonable distinction.

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 usage for setting form field values but does not provide explicit guidance on when to choose this tool over alternatives such as browser_type or browser_click. There are no when/when-not or alternative mentions, so it falls to the agent to infer context.

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