wb_fill

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

The description discloses the core behavior of clearing existing content before filling, which is important for a mutation tool. It also explains the selector format ('@e or CSS'), which is useful. However, it doesn't mention potential side effects like triggering input events or requiring element visibility, and there are no annotations to fall back on.

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 extremely concise and front-loaded. Two short sentences communicate the main action and the crucial selector syntax without any unnecessary words. Every part earns its place.

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?

For a simple fill tool, the description provides essential information but lacks details about return values, error conditions, or timing. It also doesn't mention the 'session' parameter. With no output schema and no annotations, the description is adequate for basic use but not fully complete for an agent making decisions.

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 'value' with a description and 'selector' with minLength, but not the 'session' parameter. The description adds meaning to 'selector' by specifying '@e' or CSS, which is beyond the schema. However, it doesn't explain 'session', and with 67% schema coverage, the description only partially compensates for the gap.

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 'Clear-and-fill' and the target resources 'input/textarea/contenteditable'. It distinguishes from sibling tools like wb_click or wb_get_text by focusing on filling form elements. However, it doesn't explicitly differentiate itself from similar tools like wb_upload or wb_press_key, so it's not a full 5.

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 filling input fields but does not provide explicit when-to-use guidance or alternatives. There's no mention of when not to use this tool (e.g., for file uploads) or which sibling tool might be more appropriate for other scenarios.

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