screen_info

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

With no annotations, the description carries the burden. 'List' clearly signals a read-only operation, and it details what data is returned (display id, bounds, main flag, mouse position). It doesn't discuss coordinate systems or live-update semantics, but for a simple informational tool, the behavioral disclosure is adequate.

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?

A single, well-structured sentence that front-loads the action and lists the exact information returned. No filler or redundant wording.

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 low complexity, zero parameters, and no output schema, the description fully explains what the tool returns. It covers both the display details and mouse position, making it sufficient for an agent to select and invoke the tool correctly.

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 tool takes zero parameters, so there is nothing to document. The baseline for 0-parameter tools is 4, and the description appropriately adds no parameter information because none exists.

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 the specific verb 'List' with a clear resource ('displays') and details the output fields (id, bounds, main) plus the current mouse position. This clearly distinguishes it from sibling tools like mouse_move and mouse_click, which are action-oriented rather than informational.

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 clearly implies when to use the tool: when you need display configuration or the current mouse position. It doesn't explicitly mention alternatives or exclusions, but the context is unambiguous because no other sibling tool provides this kind of system information.

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