ai_screen_elements

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains the underlying mechanisms (accessibility tree for native apps, Chrome DevTools Protocol for web), describes the exact return format (annotated screenshot, element list, web: prefixes), and states the accuracy advantage. This is rich, non-obvious behavioral context that goes well beyond a basic summary.

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 front-loaded with the key usage directive and organized with numbered return points, making it scannable. It is slightly repetitive in its preference messaging ('PREFERRED', 'Always prefer this') and has some promotional tone, but each sentence still contributes useful information.

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 provides a complete picture: what it detects, how it detects it across native and web contexts, what it returns, how results are formatted, and why its coordinates are preferable. An agent has enough information to select and invoke this tool correctly without further guessing.

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 description coverage is 100%, so both parameters (pid and maxWidth) are already fully documented in the input schema. The tool description adds no additional parameter-specific semantics, which matches the baseline score of 3 for high schema coverage.

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 auto-detects all interactive UI elements and returns an annotated screenshot plus a numbered element list with center coordinates. It differentiates itself from manual screenshot coordinate guessing and makes its scope ('when you need to click or interact with UI elements') immediately apparent, even though it doesn't explicitly contrast with named sibling 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?

It gives explicit usage timing: 'Use this FIRST when you need to click or interact with UI elements' and 'Always prefer this over screenshot+manual coordinate guessing.' This provides clear context for when to use it, but it does not mention when not to use it or name alternative tools such as ai_find_element or accessibility_tree.

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