left_mouse_down

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

With no annotations, the description must carry the behavioral burden, and it does disclose the essential trait: the button remains held and must be released by a subsequent left_mouse_up. It does not describe side effects or return behavior, but for a low-level mouse action the core behavior is covered.

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 one efficient sentence plus the critical follow-up constraint. Every word earns its place and the key behavior is front-loaded.

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 the tool being simple, the nested target parameter is left entirely unexplained at 0% schema coverage, and there is no guidance on how target relates to sibling operations. An agent would likely need more detail to construct a valid call.

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 schema has 0% description coverage, and the description does not explain the target object or its type/index/state_id fields. 'At a target' merely restates the parameter name without specifying valid values or how to construct the object.

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 uses a specific verb ('press and hold') and resource ('left mouse button at a target'), and the 'Must be followed by left_mouse_up' sentence distinguishes it from siblings like left_click and double_click. This is immediately identifiable.

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?

It clearly states the required follow-up action, left_mouse_up, which is important usage guidance. It does not explicitly contrast with alternatives such as left_click or left_click_drag, but the pairing instruction provides clear context.

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