screenshot_virtual_display

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

Annotations already mark the tool as readOnlyHint=true and destructiveHint=false, indicating safe read behavior. The description adds that it captures the entire display and returns a JSON with dimensions, but no side effects are mentioned. With annotations covering the safety profile, the description provides modest additional context.

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 concise with two sentences plus an Args/Returns section, front-loading the action. Every sentence is functional, though the Args section could be integrated to reduce verbosity.

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 explains the return format and scope (whole display) but omits prerequisites (e.g., virtual display must exist) and error conditions. Given the tool's simplicity and the presence of an output schema, it is adequate but not fully 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 description lists the two parameters (display number and output path) but does not add detail beyond what the input schema already provides (defaults, ranges, descriptions). With schema description coverage at 0% (though nested properties have descriptions), the description provides minimal extra meaning.

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 'Capture the whole Xvfb virtual display to a PNG' with a specific verb and resource, distinguishing it from the sibling 'screenshot' tool which likely captures the physical display. It leaves no ambiguity about the tool's function.

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?

No guidance is provided on when to use this tool versus alternatives (e.g., the plain 'screenshot' tool) or prerequisites (e.g., virtual display must exist). The description implies it is for Xvfb displays but does not explicitly state usage contexts.

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