screenshot

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

The description adds substantial behavioral context beyond the annotations: it reveals that window capture uses Win32 PrintWindow and works even when the window is not focused, hidden, or on a headless desktop. This goes beyond the simple readOnlyHint and destructiveHint, giving the agent critical expectations about the tool's capabilities.

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 well-structured with a clear purpose statement, a dedicated 'BACKGROUND CAPTURE' section, and a concise Args/Returns summary. Every sentence adds value, and the entire text is appropriately sized for the tool's complexity.

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 main behavior, background capture, and return format. It includes the output JSON structure (ok, path, width, height), which complements the output schema. However, it doesn't mention any prerequisites or limitations (e.g., platform-specific behavior beyond Linux display), so it's not fully complete but is sufficient given the schema richness.

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 'Args' line provides only a high-level summary ('monitor index, optional region, output path, optional window target and client_only flag') and doesn't explain the individual parameters in detail. The schema itself has rich descriptions for each parameter, but the description adds little beyond that. With schema description coverage reported at 0%, the description fails to compensate for the gap.

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 captures a screenshot of a monitor or pixel region and saves as PNG. It uses a specific verb ('Capture') and resource ('screenshot'), which distinguishes it from generic operations. However, it doesn't explicitly differentiate from the sibling tool 'screenshot_virtual_display', so it falls 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?

The description provides strong usage context, particularly the 'BACKGROUND CAPTURE' section, explaining when to use window capture (unfocused, hidden, off-screen) via hwnd or window_title. It doesn't explicitly mention when to use this tool over alternatives like screenshot_virtual_display, so it lacks an explicit exclusion, but the context is clear.

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