qemu_screen_capture

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

Annotations already signal read-only and non-destructive behavior. The description adds a non-obvious side effect: the VM remains locked by the session and requires vm_unlock. This is valuable transparency beyond the annotations, though it does not describe error states or what happens if the controller has already started.

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 what the tool does and when, the second discloses the locking behavior and required next step. No wasted words, all content is relevant and 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?

The description covers purpose, timing, and lock behavior, but with no output schema it fails to explain what the capture returns (e.g., image data, file path). It also omits error behavior for invalid timing (after controller start) or already-locked VMs. Adequate for a simple tool but leaves important usage gaps.

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?

Schema description coverage is 0%, and the description does not mention vm_id at all. The parameter name and pattern in the schema provide some basic meaning, but the description adds no additional context about how to identify the VM or any special format requirements beyond the pattern.

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 a specific verb ('Capture') and resource ('QEMU framebuffer') with a precise timing condition ('before the Windows controller has started'). This distinguishes it from the generic 'screen_capture' sibling and other QEMU tools.

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?

It provides a clear precondition ('before the Windows controller has started') and a required follow-up ('call vm_unlock when finished'). However, it does not explicitly mention when not to use it or contrast with alternative tools like screen_capture, which would strengthen the guidance.

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