fill_form

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

With no annotations at all, the description carries the full disclosure burden, and it does well: it reveals supported element types (text inputs, textareas, checkboxes, radio buttons, selects), checkbox value semantics (true/false), and the optional side effect of clicking a submit button — a mutation risk the agent should know about. Minor omissions (behavior on unsupported elements, whether existing values are cleared) keep it from a 5.

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 short, dense sentences with zero filler. The purpose is front-loaded, the value-format semantics are compressed into one informative sentence, and the optional submit side effect gets its own sentence. Every line 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?

The tool is moderately complex — 4 parameters, a nested object, multiple supported field types, no output schema, and no annotations — so the description must do more than it does. The core fill-and-submit flow is covered, but the locator strategy (by), timeout semantics, and failure behavior are absent. An agent could invoke it correctly for the happy path but would be under-informed about configuration options.

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 50%: fields and submit have descriptions, but by and timeout are bare. The description adds meaning for the fields map (selector-to-value, checkbox true/false, select by visible text or value), partly duplicating the schema, but it never explains what the `by` parameter controls (despite asserting CSS selectors while a default strategy parameter exists) or what `timeout` governs. The gaps leave the agent guessing about two of four parameters.

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 opens with a specific verb and resource: 'Fill multiple form fields in a single call.' It clearly distinguishes itself from single-element siblings like type_text, click, and clear_field through the emphasized batching aspect. It stops short of a 5 because it never names a sibling explicitly, leaving the differentiation to inference.

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 usage context is implied rather than stated: filling multiple fields at once, with automatic handling across input types, suggests when it beats type_text or select_option. However, there is no explicit when-not guidance, no mention of preferring type_text for a single field, and no prerequisites stated (e.g., form must be present, page must be loaded). It is usable but relies on the agent inferring the boundary conditions.

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