take_screenshot

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

The readOnlyHint annotation already declares this is a safe read operation, so the bar is lower. The description adds that it returns a PNG image, which is a useful behavioral detail. However, it does not disclose potential limitations such as screen lock state, permission requirements, or what happens if no phone is connected.

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 zero wasted words. It front-loads the core action ('Take a screenshot') and follows with the output format. Highly efficient.

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 parameterless, read-only tool with a clear purpose and stated output format (PNG), the description is reasonably complete. There is no output schema, but the description addresses the return type. Minor gaps around failure conditions exist, but they don't substantially impede correct tool usage.

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?

There are 0 parameters, so the schema carries no burden and the description doesn't need to explain any. With no parameters to document, the baseline of 4 applies. The description correctly focuses on behavior and output rather than parameter details that don't exist.

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 the action (take a screenshot), the target resource (connected phone screen), and the output (PNG image). It distinguishes itself from siblings—none of which relate to screen capture—so there is no ambiguity about what this tool does.

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 description implies when to use it (when a screenshot of the phone is needed) but does not explicitly name alternatives or exclusion conditions. There is no guidance about prerequisites like device connection state, which the sibling get_device_status might help verify. However, the purpose is clear enough that an agent can infer appropriate usage.

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