press_key

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

No annotations are present, so the description carries the burden of explaining behavior. It clearly enumerates the accepted keys and modifier names, providing an exhaustive list that goes beyond any structured data. It does not describe side effects like whether the key is pressed and released, but for a simple key-press tool, the list of valid inputs is strong disclosure. It does not contradict any annotations (there are none).

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 concise sentences. The first sentence states the core function, and the second sentence lists the supported keys and modifiers in a compact, scannable format. Every word earns its place; there is no fluff or repetition.

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 two-parameter tool with no output schema, the description is highly complete. It fully covers the allowed input space for both parameters. It does not mention return values, error behavior, or target focus, but these are arguably not essential for a key-press tool. The lack of annotations is compensated by the explicit key/modifier lists, making this close to fully contextual.

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 input schema covers 100% of parameters with descriptions and examples, which earns a baseline of 3. The description adds meaningful value by enumerating the full set of valid key names (return, tab, space, escape, delete, arrows, home/end, pageup/pagedown, a–z, 0–9) and modifier names (cmd, shift, alt, ctrl). This transforms the schema's generic examples ('return', ["cmd"]) into a complete vocabulary guide.

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 opens with a specific verb and resource: 'Press a key with optional modifiers.' It distinguishes itself from sibling tools by listing the exact supported keys and modifiers, which separates it from type_text (typing text) and mouse actions. The scope is clear: individual key presses with keyboard shortcuts in mind.

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?

Usage context is implied rather than explicitly stated. The list of non-character keys (arrows, return, tab, etc.) suggests this is for shortcuts and navigation keys, and 'type_text' exists as a sibling tool for typing strings. However, there is no explicit 'when to use this' vs. alternatives, no mention of keyboard focus requirements, or when not to use it.

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