browser_mouse_down

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

Annotations already indicate destructiveHint=true and readOnlyHint=false, signaling a state-changing action. The description adds no extra behavioral context beyond what the annotations provide, such as that the button remains pressed until a mouse_up event.

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 extremely concise at three words, leaving no unnecessary text. It is direct and front-loaded, efficiently conveying the core action.

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?

Given the simplicity of the tool (one optional param, no output schema), the description is too minimal. It fails to explain that the mouse button is held down until a complementary action (like mouse_up), and it does not relate to the coordinate-based siblings. This leaves the agent without crucial context for proper use.

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% with a well-described enum parameter for button. The description does not mention the parameter, but the schema already handles it. Baseline 3 is appropriate since the description adds no additional meaning beyond 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?

The description 'Press mouse down' clearly identifies the action as a mouse press event. It is specific enough to distinguish from sibling tools like browser_mouse_up or browser_click, but it does not explicitly state that it is a press without release, which could be ambiguous.

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?

There is no guidance on when to use this tool versus alternatives like browser_mouse_click_xy or browser_drag. No context is provided about typical usage patterns (e.g., pairing with mouse_up) or when to prefer this over a higher-level click.

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