fill_form_field

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

With no annotations provided, the description must disclose side effects and behavior. It only says 'fill', omitting details such as whether it triggers events, overwrites existing values, or handles disabled fields. An agent cannot predict the tool's full impact.

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 concise sentence with no wasted words. However, it could be restructured to front-load more critical information or be expanded slightly without losing conciseness.

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 the tool's simplicity and lack of output schema/annotations, the description should cover return behavior and constraints. It does not mention return status, error conditions, or support for different input types, leaving the agent with significant unknowns.

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 both parameters (selector and value). The description adds no additional meaning beyond what is in the schema. Baseline of 3 is appropriate as it does not detract but does not enhance understanding.

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 verb (fill) and resource (form field), and implies the tool is for entering values into form inputs. It distinguishes from siblings like click_element and submit_form by specifying a different action. However, it could be more specific about the mechanism (e.g., typing vs setting value via JavaScript).

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?

No guidance is provided on when to use this tool versus alternatives. It does not mention prerequisites (e.g., element must be visible) or when not to use it (e.g., for non-input elements). Sibling tools like click_element are not contrasted.

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