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

Adds substantial context beyond the annotations: keyboard-level behaviours, a hard refusal rule for Enter on account pages, the return values (URL and title), and session economics (credits per started minute, idle timeout of 3 minutes). It does not explain why the operation is flagged destructive or what a keypress might trigger, so it stops short of fully covering the destructiveHint=true annotation.

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 core action, then key examples, then constraints and cost. Dense but every sentence carries information; the credit/session sentence is long but operationally relevant rather than filler.

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?

Despite having no output schema, the description states what is returned, covers the safety-relevant refusal, and discloses cost and session lifetime. An agent has everything needed to invoke this correctly in the Substack Cloud Browser context.

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 enumerates all 15 allowed keys, so the baseline is 3; the description earns an extra point by explaining what the most important keys actually do and by documenting a per-key constraint (Enter refused on account pages) that appears nowhere in 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 ('Presses one key on the current page') and scopes it precisely to the focused element, which cleanly separates it from cotlet_browser_click and cotlet_browser_type. Concrete key-to-outcome examples (Tab to next field, Enter to send, arrows for suggestion lists) make the intent unmistakable.

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 situational examples of when to press keys rather than click or type, plus an explicit exclusion ('Enter on account pages is refused'). It does not name sibling tools as alternatives, but the usage contexts are strong enough that an agent can pick correctly.

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