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

Annotations are all false, providing no safety profile, so the description carries the burden. It discloses a key behavior: operations return pixels without interacting with the visible UI. It does not mention that take_screenshot writes a temporary PNG and deletes it unless keep=true, but that is documented in the schema's parameter description and the description is not misleading.

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 sentences, front-loaded with the core purpose and scoping, then the alternative routing. Every word earns its place; there is no filler. The structure makes the decision point immediately clear.

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 three operation branches and many selectors, the description covers the primary decision (pixels vs. semantics/action) and names the operation families. An output schema exists, so return values don't need explanation. It doesn't enumerate all parameters, but the schema does, and the description is sufficient for correct invocation.

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 coverage is 100%, so the baseline is 3. The description maps operations to pixel outputs but adds no details about parameters such as path, keep, directory, or the screenshot_region selectors. The schema already documents all parameters thoroughly, so the description adds little beyond operation-level context.

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 states a specific verb+resource: returns pixels by reading an image or capturing the desktop, window, monitor, or region. It explicitly distinguishes from control_computer and control_browser, which handle semantic structure or actions. The three operations are clearly implied and the intent is unambiguous.

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 explicitly states when to use the tool: 'when the result must be pixels from a paired computer.' It names the alternatives (control_computer, control_browser) and the exact condition under which they should be used instead. This leaves no ambiguity about tool selection.

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