screenshot

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

With no annotations, the description carries the full burden, and it does disclose the output format (JPEG), the default device width (1080), and the important behavioral consequence that coordinates derived from the image must be scaled back. It omits whether the full screen or a cropped region is captured, and any size/rate limits.

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, tightly packed sentence: what is returned, how it is sized, and the practical implication for coordinates. Nothing is wasted and the return format 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?

For a one-parameter, read-only capture tool with no output schema, the description covers the essentials: format, sizing, and coordinate mapping. A brief note on screen coverage or how it differs from sibling visual tools would make it complete.

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 description coverage is 0%, so the description must explain the single parameter, and it does: 'width' is the target pixel width, with the note that the device is usually 1080 wide and that coordinates must be scaled back. That adds meaning well beyond the bare integer schema and default of 540.

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 states a concrete resource and result: 'Current screen as JPEG', so an agent knows immediately this captures a visual snapshot. It does not explicitly distinguish itself from the sibling 'observe' tool, which likely also returns screen state, leaving some ambiguity about which to pick.

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?

Usage is only implied: the note about scaling coordinates back hints that this tool is used to locate elements before tapping. There is no explicit statement of when to use this versus 'observe' or when to prefer text-based element lookup over a pixel screenshot.

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