Screen size

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

Annotations already mark it readOnly, idempotent, and non-destructive; the description adds behavioral output context by defining the returned coordinate space as global point bounds and including scale and main. This is useful for interpreting values for downstream tools like click or move_mouse.

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 sentence that fronts the return content and appends the use case, with no filler, tautology, or repetition of the title. Every clause earns its place.

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 no-argument, read-only utility the description fully covers what an agent needs: what is returned, the coordinate system, and why to call it. The inline field list compensates for the lack of an output schema.

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 has zero parameters, so schema coverage fully documents the input surface. Per the baseline for 0-parameter tools, a 4 is appropriate; the description correctly avoids inventing parameter guidance.

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 an explicit verb ('Return'), a specific resource (overall desktop size + every display's bounds), and enumerates fields (origin x/y, width, height, scale, main). This differentiates it from visual tools like screenshot or filesystem tools like read_file by focusing on coordinate geometry.

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?

Directly tells the agent when to use it: 'use it to reason about click coordinates across monitors.' It doesn't name excluded alternatives, but the stated use case is specific enough to steer selection among siblings like click, move_mouse, and screenshot.

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