observe_screen

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

With no annotations, the description carries the full burden and explains the main behavioral traits: the response is textual, screenshot inclusion is controlled by include_screenshot, and when enabled the screenshot is delivered as a separate message. It does not explicitly state that the operation is read-only or describe failure modes, but the observe semantics and returned-state detail are reasonably transparent.

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 compact and front-loaded, with the core 'one call collects screen state' statement first. Each of the four sentences adds useful information, though bullet points would improve scannability.

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 no output schema and no annotations, the description explains the returned payload and screenshot behavior well. However, it omits the role of serial and does not mention device prerequisites or error behavior, leaving some operational context unresolved.

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?

Parameter schema coverage is 0%, so the description must compensate. It explains include_screenshot and its behavior, but the serial parameter is never mentioned or semantically defined, leaving a significant gap for how the agent targets a device.

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 clearly states that the tool collects the current screen state in one call, listing the exact returned data: foreground app/activity, screen size and orientation, and key clickable/editable UI elements. It also distinguishes itself from siblings by naming foreground_app, ui_dump, and screen_state as the tools it replaces.

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 gives clear usage context: use this composite tool before steps to avoid multiple separate calls, and names the sibling tools it consolidates. It does not explicitly state when not to use it or when a specialized tool would be better, so it stops short of a full 5.

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