Screenshot Region

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

Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds valuable transparency by specifying that it uses grim (Wayland wlroots screencopy) and returns the image as base64, but it does not disclose potential errors or side effects beyond what annotations cover.

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 two concise sentences with no filler. It efficiently conveys the core functionality, coordinate system, and output format, making it easy to scan and understand.

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 that no output schema is provided, the description's note about returning the image inline as base64 is essential context. It also clarifies the coordinate system (layout pixels). However, it lacks information about error handling or edge cases (e.g., out-of-bounds coordinates), which prevents a perfect score.

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?

All parameters (x, y, width, height, scale, include_cursor) have clear descriptions in the schema, covering 100% of the input semantics. The description adds no additional parameter information, so the baseline score of 3 applies.

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?

Description clearly states it captures a rectangular screen region via pixel coordinates, explicitly differentiating from sibling tools like screenshot_window (window capture) and screenshot_fullscreen (fullscreen capture). The verb 'Capture' and specific resource 'rectangular screen region' make the purpose unambiguous.

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?

Description mentions pixel coordinates and base64 output, but does not explicitly state when to choose this tool over alternatives like screenshot_window or screenshot_fullscreen. The coordinate-based approach implies region capture, but there is no direct 'use when' or 'use instead' guidance.

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