press_key

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

With no annotations provided, the description carries the full burden. It lists the keys but does not disclose potential side effects (e.g., power toggling screen) or mention device prerequisites. The key names imply behavior, but no additional context is given.

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?

A single sentence that is front-loaded with the action and immediately lists the supported keys. No unnecessary words or repetition; the format is efficient and easy to scan.

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?

The tool is simple, with two parameters and an existing output schema. The description provides the essential key list, and the schema covers parameter details. It does not explain return values, but the output schema handles that, so the description is adequately complete.

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?

The schema covers both parameters syntactically, but the description adds value by enumerating all valid key values (back, home, recent, etc.) that the schema does not explicitly list, only giving an example. This compensates for the lack of an enum.

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 verb ('Press') and resource ('system key'), and enumerates all supported keys, making it distinct from sibling tools like tap, type_text, and swipe.

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 usage: use this tool to press system keys rather than screen taps or text input. It does not explicitly mention exclusions or alternatives, but the clear resource scope provides sufficient context.

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