screen_capture

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

Beyond the annotations (readOnlyHint=true, idempotentHint=true, destructiveHint=false), the description discloses a significant side effect: acquiring the VM lease and leaving the VM locked until vm_unlock is called. It also specifies the output format as native MCP PNG image content, adding valuable behavioral detail.

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 two sentences with no filler. It front-loads the primary purpose and immediately follows with the essential locking caveat. Every sentence earns its place.

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 tool has a nested schema, no output schema, and moderate complexity. The description covers the core behavior, output format, and locking side effect. It is mostly complete, but the missing include_cursor parameter semantics prevent it from being fully self-sufficient for an 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 schema has 0% description coverage, so the description must explain parameters. It clarifies that the region parameter is optional (capture primary display vs. a pixel region), but it does not mention the include_cursor parameter at all, nor does it explain the region object's width/height semantics beyond what the schema already provides.

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 opens with a specific verb and resource: 'Capture the primary display or a pixel region as native MCP PNG image content.' This clearly distinguishes it from sibling tools like window_capture, which targets windows, and clipboard_get, which targets clipboard content.

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 provides clear context for when to use the tool (capturing a display or pixel region) and adds critical operational guidance about the VM lease. However, it does not explicitly name alternatives such as window_capture or state when not to use this tool, so it stops short of a perfect score.

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