browser_fill_form

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

With no annotations, the description carries the full burden. It adds useful behavior context (supported element types, optional post-fill submit) that goes beyond the schema, but omits failure handling for invalid refs/selectors, partial-fill behavior, and any return/confirmation semantics for a mutating 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?

Four sentences with zero waste, ordered purpose-first, then capability, then differentiation, then the optional side effect. Every sentence 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 browser form-fill tool with no output schema and no annotations, this covers the core behavior, the batch advantage, and the submit option. It is largely complete, with only error/partial-failure behavior unaddressed.

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 fields, ref, selector, clear, and value. The description reinforces the submit parameter ('optionally submit the form after filling') but adds no syntax or format detail beyond the schema, matching the baseline 3.

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?

States a specific verb and resource (fill multiple form fields in a single call) and explicitly differentiates from the sibling browser_type by noting it reduces round-trips. It also enumerates the supported element types, so an agent can identify the tool without opening any schema.

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?

Clearly frames the batch-fill use case and names the alternative it replaces (calling browser_type per field). It gives a strong context signal for when to prefer this tool, though it does not state when NOT to use it or any prerequisites (e.g., needing refs from a snapshot).

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