screenshot_app

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

readOnlyHint=true is consistent with a capture operation. The description adds a real behavioral constraint not present in annotations: the tool will not work when no window exists. It omits details such as image format, resolution, or how the failure manifests, which keeps it short of a 5.

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 short sentences, with the purpose front-loaded and the caveat second. Nothing is redundant or padded.

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 parameterless read-only capture tool with no output schema, the description covers what it returns (an image of the window) and the one condition under which it fails. It could say slightly more about the resulting image or error behavior when no window exists.

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 the schema imposes no semantic burden and the baseline is 4. Nothing in the description is needed to explain inputs.

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 and resource — capturing the app's window as an image — and adds the intent (to check what the user is seeing). No sibling tool does anything similar, so it is trivially distinguishable from the arrangement/playback/instrument tools listed.

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?

"To check what the user is seeing" gives a clear condition for use, and "Not available without a window" states a precondition. No exclusion or named alternative is given, but no sibling is a plausible substitute for visual capture.

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