fill_by_label

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

With no annotations, the description carries full burden. It discloses that the tool finds the associated input/textarea, fills it, supports React/Vue/Angular, and lists available labels on failure. This is informative but could detail side effects or required page state.

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?

Three concise sentences, front-loaded with the core purpose. Every sentence adds value—purpose, method, framework support, and debugging help—with no redundancy.

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 lack of output schema, the description covers the core functionality and error handling. It is sufficient for a simple fill tool, though it could mention preconditions like page load or field visibility.

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 coverage is 100%, but the description adds value by noting that the 'label' parameter uses case-insensitive partial matching, which is not in the schema. This enhances understanding beyond the basic schema descriptions.

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', the resource 'form field', and the method 'by its label text'. It distinguishes from sibling tools like 'type_text' or 'click_element' by specifying the label-based approach and mentioning framework compatibility.

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 form fields with labels and works with modern frameworks, but it does not explicitly state when to use this tool versus alternatives like 'type_text' or 'click_element'. No when-not guidance is provided.

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