screenshot

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

No annotations, so the description carries the full burden. It usefully discloses the default scaling behavior and the resulting coordinate correspondence, but says nothing about what is actually returned (image payload, dimensions), whether it fails on a non-booted device, or any cost/latency of full-res capture.

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, purpose front-loaded, with the behavioral caveat second. No filler, nothing repeated from the schema.

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 zero-annotation, no-output-schema tool, the description covers the coordinate semantics well but leaves the agent guessing about the return value and about session/device readiness requirements, which matter for calling it correctly in a device-control workflow.

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 baseline is 3; the description earns above that by making the implicit default explicit — that scaling to screen points is the default state of fullRes=false and why it matters (pixel coords equal tap coords). It does not discuss the device parameter's fallback chain, but the schema already documents that fully.

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 and resource ('Take a screenshot') immediately, with an added scope note about output scaling. It does not differentiate itself from the overlapping sibling describe_ui, which also returns visual state, but the core purpose 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?

The coordinate-equivalence note implies the intended workflow (screenshot before tap), but the description never says when to use this versus describe_ui or list_devices/select_device, and gives no prerequisites such as needing a started session.

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