Capture VM Screen

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

With no annotations provided, the description carries the burden of behavioral disclosure. It discloses the return/save behavior and the credential requirement, which go beyond the tool name and input schema. It stops short of detailing side effects of saving to host_path or setup implications of guest credentials, but the core behavior is 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?

Two concise sentences: the first states the action and output format, the second states the alternative save behavior and key prerequisite. All information is front-loaded and there is 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?

The description covers the core invocation aspects: target VM, optional host path, output handling, and credential prerequisite. However, it does not clarify the apparent optionality of vm given the schema reports no required parameters, nor does it explain how guest credentials are configured. This leaves some correctness ambiguity for an autonomous agent.

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 input schema already documents both parameters fully, including the host_path fallback behavior. The description reinforces the output format (base64 PNG) but adds no meaningful new semantics for the vm parameter, so the baseline score of 3 applies.

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 states a specific action and resource: 'Capture a screenshot of the VM screen.' It further distinguishes the tool by explaining output behavior (base64-encoded PNG vs. saving to a host path), so there is no ambiguity about what it 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 gives a prerequisite ('Requires guest credentials in config') and indicates when saving vs. returning output is used, but it does not explicitly state when to prefer this tool over alternatives. There are no screenshot-related siblings, so usage context is mostly implicit.

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