screenshot

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

No annotations exist, so the description carries the burden. It usefully discloses the pixel-to-window coordinate conversion returned with the image, which is real behavioral context beyond the schema. However it says nothing about whether restore mutates window state, cost/latency, or what the payload actually looks like, leaving mutation-side effects to the schema.

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?

Two sentences, both front-loaded and load-bearing: the first defines what is captured, the second gives the coordinate-mapping fact needed to act on the result. No filler.

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?

With no output schema, the description does the important work of hinting at the return payload (image plus window_units_per_pixel). It stops short of confirming the image encoding or how element refs are surfaced, but nothing essential for calling the tool is missing.

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 80%, so the schema already documents ref, window, restore and max_width; the description only echoes the ref-based element capture. It also names window_units_per_pixel, which is not in the input schema at all, so the agent could mistake it for a parameter rather than an output field.

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 specific verb+resource ("Capture a Cascadeur window ... as an image") and covers both scope variants: whole window or a single element by ref. That clearly separates it from the UI-driving siblings such as ui_click or ui_tree, which read/inspect rather than render pixels.

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?

Implicitly routes the agent into the screenshot-then-click workflow by explaining that window_units_per_pixel converts image pixels to the coordinates ui_click expects. There is no competing screenshot sibling, so no explicit exclusion is needed, but it never states plainly when to reach for this tool (e.g. after ui_tree fails to identify an element).

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