Screenshot a simulator or device

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

With readOnlyHint=true already telling the agent this is a safe read, the description adds real behavioural context: full resolution, no window chrome, and the implicit prerequisite that a simulator must be booted or a device connected. It stops short of saying how the image is returned (inline vs file path), which would be the remaining useful disclosure.

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 tight sentences, front-loaded with the core action and scope, then the usage hint. Every clause earns its place with no redundancy.

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 single-parameter read tool with no output schema, the description covers target, resolution, chrome behaviour and usage intent. The only real gap is how the capture is delivered back (inline image vs saved path), which the absent output schema leaves to the description.

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 0% and the schema only lists the enum values, but the description meaningfully maps them: platform ios = booted iOS Simulator, platform android = connected Android device/emulator. That is genuine semantic value beyond the bare enum, though it omits the default ('ios').

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 action (full-resolution screenshot) and its exact resource (booted iOS Simulator or connected Android device/emulator), plus the 'without window chrome' scope qualifier. An agent can distinguish this from browser/window capture siblings such as look or list_windows without opening any schema.

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?

'Use it to explain or debug app UI, then find the view in code' gives clear positive context for when to reach for this tool. It does not name alternatives or state exclusions (e.g., when to prefer browser_* or look instead), so it stops short of full when/when-not routing.

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