browser_key_down_up

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

Annotations already declare readOnlyHint=false and destructiveHint=true, but the description adds no further behavioral context. It does not explain why the action is destructive, whether events are trusted, or what side effects might occur, so it fails to build on the annotation baseline.

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?

The description is a single, clear sentence that is front-loaded and free of filler. Every word contributes to the meaning, making it highly concise and well-structured.

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 simple 2-parameter tool with complete schema and some annotation coverage, the description is adequate but has gaps: it does not explain return values, behavioral effects, or when to prefer this over sibling tools. It is minimally complete but could be improved with usage 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?

The input schema provides 100% coverage with clear descriptions for both parameters (key and action). The tool description adds no additional meaning beyond what the schema already documents, so the baseline of 3 is appropriate.

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 clearly states it fires a keydown or keyup event for custom key combinations or modifier actions, using a specific verb+resource. It differentiates from siblings like browser_press_key (full press) and browser_type (typing) by focusing on separate keydown/keyup events.

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 description implies usage for custom key combinations or modifier actions but does not explicitly state when to use this tool versus alternatives like browser_press_key or browser_dispatch_event. No exclusions or preference guidance are provided.

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