Capture Window

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

The description goes well beyond the annotations by disclosing a prerequisite (Screen Recording permission) and a fallback mechanism (`screencapture -l`) with a detail about how the raw windowId is reused. This is rich behavioral context that is not present in the readOnlyHint/destructiveHint annotations, making the tool's runtime behavior more transparent.

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 sentences with no wasted words. It front-loads the core purpose and then efficiently adds permission, fallback, and handle details. Every sentence carries meaningful information, and the structure is easy to parse.

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?

The description covers the essential aspects: purpose, input source, permission, and fallback. However, since there is no output schema, it does not specify the return format (e.g., image path, data URL). This is a minor gap, as the behavior is otherwise thoroughly documented, but it 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?

The schema already provides descriptions for both parameters (100% coverage), so the baseline is 3. The description adds extra meaning by explaining that the windowHandle contains a raw windowId that is reused in fallback mode, which gives the agent a deeper understanding of the handle's internal structure. It also reinforces the relationship to list_capturable_windows.

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 clearly states the tool's purpose with a specific verb ('Take a screenshot') and resource ('a single window'), and distinguishes it from sibling tools like capture and capture_region by specifying that it operates on a window identified by a windowHandle. This is a precise, action-oriented description that leaves no ambiguity about what the tool does.

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?

The description provides clear usage context by referencing list_capturable_windows as the source for the handle, and it explains the fallback behavior when the helper is unavailable. However, it does not explicitly contrast this tool with alternatives such as capture (full screen) or capture_region, so the when-not-to-use guidance is implicit rather than explicit.

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