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

Goes well beyond the annotations by disclosing the return payload (URL and title), the refusal rule for Enter on account pages, the credit cost per started minute, and the session lifecycle (ends on close or 3 minutes after the last call). The annotations carry only safety hints, so this behavioral detail is genuinely additive.

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?

Front-loaded with the action and outcome examples, then constraint, then return value, then cost model — a sensible ordering with no filler. The final sentence is long and packs cost plus session timeout together, which is slightly dense but each clause carries information.

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 supplies the return value, and it covers the operational facts an agent needs for a stateful, credit-metered browser session: refusal conditions, session expiry, and cost. Nothing material for correct invocation is missing.

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% and the enum already enumerates the 15 allowed keys, so the baseline is 3. The description adds real semantics by explaining what several of those keys accomplish in context (Tab advances fields, Enter submits, Escape dismisses dialogs, arrows move through suggestions), which helps an agent choose the right enum value.

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 ('Presses one key on the current page... on the element that has focus') and immediately grounds it with concrete outcomes (Tab to next field, Enter to send, Escape to close a dialog). The focus-target wording separates it from cotlet_browser_click and cotlet_browser_type, which act on selectors or insert text.

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?

Gives clear usage context through key-by-outcome examples and a hard constraint ('Enter on account pages is refused'), which tells the agent when this call will fail. It does not explicitly route to alternatives like cotlet_browser_type for typing text or cotlet_browser_click, so it falls short of a full when/when-not treatment.

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