capture_region

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

No annotations are provided, so the description carries the full burden. 'Global compositor coords' is a useful hint about the coordinate space, but it says nothing about permissions, whether overlays/HiDPI scaling are handled, out-of-bounds behavior, or what the capture returns.

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 tight sentence with the coordinate-space constraint front-loaded. No wasted words.

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?

An output schema exists so return values need not be explained, but with four required params at 0% schema coverage and no annotations, the description should cover coordinate conventions and boundary behavior. It is too thin for the tool's complexity.

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 0% for all four required params. 'Arbitrary rectangle' and 'global compositor coords' imply x/y origin and w/h extent, but the origin corner, pixel units, and handling of negative or out-of-range values are never specified.

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 a clear verb (Screenshot) and resource (arbitrary rectangle), and the phrase 'arbitrary rectangle' implicitly separates it from the monitor/window siblings. It does not name those siblings or explicitly contrast the scope, so it lands just short of a 5.

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 when-to-use guidance and no alternatives named. The reader can infer it is used when you want a free-form region rather than a full monitor or window, but that inference is left entirely to the agent.

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