screen_capture

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

Annotations already indicate read-only, idempotent, and non-destructive behavior. The description goes beyond those by disclosing a significant side effect: it acquires the VM lease and leaves the VM locked until vm_unlock is called. This is exactly the kind of behavioral context annotations do not capture.

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 with no filler. The capture purpose is front-loaded, and the critical VM-lock side effect and unlock follow-up are stated immediately. Every sentence carries operational value.

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?

For a tool with no output schema, the description correctly specifies the return format (native MCP PNG image content) and the critical lock lifecycle. It stops short of explaining coordinate origin for region and the effect of include_cursor, but those are partially covered by the schema and the default value.

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 only 33%, and the tool description adds no parameter-specific guidance for region, vm_name, or include_cursor. The phrase 'pixel region' weakly relates to the region object, but it does not explain semantics, defaults, or how include_cursor affects output.

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 names a specific action and resource: capture the primary display or a pixel region as MCP PNG image content. This is clear, but it does not explicitly differentiate itself from the sibling qemu_screen_capture or window_capture, both of which could overlap in 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 gives clear operational context: calling this tool acquires the VM lease and locks the VM, and the agent must call vm_unlock when finished. It does not, however, state when to prefer this tool over alternatives such as qemu_screen_capture or window_capture.

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