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 of behavioral disclosure. It does not mention potential side effects (e.g., power toggling screen, volume changes), device connection requirements, or error handling for invalid keys. The list of valid keys helps but omits any system-level impact or prerequisites.

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 a single sentence that efficiently communicates the core purpose and enumerates valid inputs. No filler words or redundant 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 simple 3-parameter tool, the description is minimally viable but leaves gaps: session_id is unexplained, and the lack of annotations increases the need for explicit behavioral context (e.g., side effects, multi-device handling). The output schema may mitigate return-value ambiguity, but the description could still offer more operational guidance.

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 description adds meaning to the 'key' parameter by enumerating all accepted values, which goes beyond the schema's single example. However, schema coverage is partial (67%): 'session_id' is left undocumented by both schema and description, and 'device' is only described in the schema. The description does not fully compensate for the missing parameter semantics.

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 (press) and the resource (system key), enumerating the specific supported keys. This unambiguously differentiates it from siblings like tap, swipe, and type_text, which operate on screen elements or text.

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 for system-level key presses, but does not explicitly contrast with alternatives (e.g., using tap for UI buttons) or define when not to use it. No exclusions or prerequisites are mentioned, leaving the decision to the agent's inference.

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