screenshot_virtual_display

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds the scope ('whole' display) and the return JSON structure (path, width, height), providing useful context beyond the annotations. No contradictions found.

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 a clear one-sentence overview followed by compact Args and Returns blocks. It is front-loaded and contains no extraneous information, efficiently conveying purpose and output.

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 core purpose, parameters, and return format, and the output schema and annotations fill additional gaps. It omits behavior when output_path is null or when the display does not exist, but given the tool's simplicity, it is largely complete.

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 provides detailed descriptions for 'display' and 'output_path', but the context signal indicates 0% parameter coverage from the description. The description merely restates 'display number and output path' without adding semantics like default behavior, constraints, or null handling, failing to compensate for the low coverage.

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 uses the specific verb 'Capture' and names the exact resource ('whole Xvfb virtual display') and output format (PNG), clearly distinguishing it from the sibling 'screenshot' tool which likely targets the main display.

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 implies use for virtual displays but does not explicitly state when to choose this over alternatives like 'screenshot' or mention exclusions. No alternative tools are referenced, so the guidance is implied rather than explicit.

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