take_screenshot

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

With no annotations, the description carries full responsibility for behavior. It discloses that the output is a large image, which is a meaningful trait, but it does not mention any other potential side effects or caveats (e.g., speed, resolution, or capture scope). For a read-only screenshot tool, this is adequate but not rich.

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 short sentences, with the core action front-loaded and the usage caveat following. Every clause serves a purpose, with no redundancy or filler.

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 simple tool with one optional parameter and no output schema, the description covers the action, the output type, and when to use it. The only minor gap is that it doesn't specify the exact format or size beyond 'large image', but that is not critical for invocation. Overall, it is sufficiently 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 input schema provides 100% coverage for the single optional device_id parameter, so the description does not need to add parameter details. It does not add any extra meaning beyond the schema, which is acceptable given the baseline of 3.

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 action ('Take a screenshot') and the subject ('device screen'), and clearly indicates the output is an image. It also differentiates from siblings by naming observe_ui / observe_webview as preferred alternatives, so an agent can distinguish this from text-extraction tools.

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?

Explicitly instructs when to use: 'prefer observe_ui / observe_webview text — use only when those cannot answer.' This gives clear conditional guidance and names the alternatives, leaving no ambiguity about selection.

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