device_unlock

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

With no annotations, the description still discloses the core behavior: it wakes the screen, unlocks with the configured PIN, and is automatically performed by UI operations. It does not cover failure modes such as a missing PIN or whether it is safe to call when already unlocked, but the core behavior is clear for a zero-parameter tool.

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 front-loaded sentence with no wasted words. The automatic UI behavior note is compactly placed in parentheses.

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 zero-parameter device action with no output schema, the description provides enough context to select and invoke it correctly. Minor gaps remain around return values and edge cases such as no configured PIN, but these are not central to invoking the tool.

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 tool has zero parameters, so the baseline is 4. The description correctly indicates that the PIN is configured rather than passed as an input.

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 names a specific action and resource: waking the screen and unlocking it with the configured PIN. It also distinguishes this tool from the ui_* siblings by stating that every UI operation performs this automatically.

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 parenthetical '(every UI op does this automatically)' gives useful context that this tool is usually unnecessary before UI interactions, implicitly reserving it for explicit unlock scenarios. However, it does not explicitly state when the tool must be used instead of relying on automatic behavior.

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