press_key

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It does not state whether the key press is injected into a specific app, whether it requires a foreground activity, whether it is synchronous, or what the return value indicates. The description is mostly a parameter list rather than behavioral context.

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 compact and front-loaded with the core purpose. The key list is long but necessary given the schema has no enums. The serial explanation is minimal. It earns its place, though the key list could arguably be trimmed by referencing Android's keycode documentation.

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 (2 params, no nested objects) and has an output schema, so the description doesn't need to explain return values. However, with no annotations and no usage guidance, an agent might not know whether pressing a key requires a focused field, whether it works on all Android versions, or what happens if the key is invalid. The key list is helpful but the behavioral context is thin.

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 0%, so the description must compensate. It does: it enumerates valid values for the key parameter and explains that raw KEYCODE_* names or numeric keycodes are accepted. The serial parameter is only mentioned as 'device serial when several are attached', which adds some context beyond the schema's bare type definition.

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 tool's purpose: pressing a hardware or navigation key. It lists the supported key names and mentions that raw KEYCODE_* names or numeric keycodes also work, which distinguishes it from sibling input tools like tap, swipe, and input_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 pressing keys, and the key list provides context for when to use it. However, it does not explicitly state when to use this tool versus alternatives like tap or input_text, nor does it mention any exclusions or prerequisites.

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