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

Annotations declare a destructive, non-idempotent, open-world write, and the description adds new behavior: it stops at the first failing field, names the fields already filled (partial-state semantics critical for a destructive tool), and never submits. It stops short of explaining why it is flagged destructive or what side effects a fill can trigger, such as conditional fields appearing.

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 tight sentences, front-loaded with what the tool does before the failure and submission caveats. The closing line ('Answers the page after it: the elements and text in view, with the same numbers') is awkwardly worded but still conveys the return shape and element-number continuity.

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?

With no output schema, the description correctly explains the return value as a page read with contiguous element numbers and covers the critical submit/no-submit distinction. The gap is risk context: nothing tells the agent a fill can irreversibly alter page state or which forms are inappropriate to auto-fill.

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%, so the schema carries the parameter documentation and the baseline is 3. The description adds useful mapping semantics — text fields take text, drop-downs an option label, checkboxes/radios/switches true or false — slightly beyond the schema's terser 'Text, option, or true/false', but dialog and dialog_text are left entirely to the schema.

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 ('Fills several fields in one step') and enumerates the widget types handled. It does not name the sibling tools it supersedes (cotlet_browser_type, cotlet_browser_select), so differentiation is inferred from 'several fields in one step' rather than stated.

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 tail gives real routing guidance: 'Does not send the form: click its button after', pointing the agent to cotlet_browser_click for submission. It implies batch filling replaces per-field typing but never states when a single-field sibling is preferable or what happens with a stale element number.

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