vm_screenshot

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

With no annotations available, the description carries the behavioral burden. It discloses the PNG return format, the requirement that the VM be running, and the purpose of observing the live console state. It does not explicitly state side effects or failure behavior, but the read-only nature is strongly implied by 'capture a screenshot.'

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 and well-structured: a single-sentence purpose, a brief prerequisite and return-type statement, usage context, and an Args block. Every part earns its place and the most important information is front-loaded.

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?

This is a simple one-parameter tool with no output schema and no annotations. The description gives the operation, the prerequisite, the return type, and representative use cases, which is enough for an agent to select and invoke the tool correctly.

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 only defines vmid as an integer, but the description adds meaning by specifying it as 'the numeric ID of the QEMU VM.' This clarifies which kind of resource the ID refers to and is sufficient for the single parameter.

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 first line states a specific action and resource: 'Capture a PNG screenshot of a QEMU VM's display.' The use cases (login prompt, GUI, boot messages) further clarify what the tool is for, and no sibling tool has the same purpose.

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 clearly states the prerequisite that the VM must be running and tells the agent to use this for viewing the current visual state of the VM console. It gives a clear context for use, though it does not explicitly mention alternatives or when not to use it.

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