Observe the active computer surface

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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so safety profile is covered. The description adds value by detailing the returned context and noting Windows-specific coverage, which goes beyond what annotations supply. Minor gap: no note on latency or that the capture is non-blocking.

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?

Three short sentences, front-loaded with the core action, with the return-content enumeration in the middle and usage guidance last. Efficient overall; "return richer context" is slightly vague but the following sentence clarifies it.

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?

With no input parameters and no output schema, the description carries the burden of describing return values, which it partially does by listing window, taskbar, monitor and application details. A note on response format or whether additional platform differences exist beyond Windows would make it fully complete.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a parameterless tool is 4. The description correctly avoids inventing parameters.

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?

States a specific verb (Capture) and resource (active desktop/browser) and enumerates the returned context (active window, taskbar rectangles, monitors, visible application windows). It is clear what the tool does, though it never explicitly distinguishes itself from the sibling mouse_screenshot, which likely also captures the surface.

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?

Gives explicit timing guidance: "Use this before visual targeting and again for verification." That tells the agent when in a workflow to call it. It lacks explicit exclusions or a named alternative (e.g., mouse_screenshot), so it earns a 4 rather than a 5.

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