lock_screen

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

Annotations only declare non-read-only and non-destructive; the description adds real behavioral context beyond them by stating that running apps are unaffected and that reversal requires a password or Touch ID. It doesn't mention auth prompts or whether other tools' state changes, but for this trivial operation the added detail is solid.

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?

Two short sentences, the action front-loaded, and the second sentence carrying only non-obvious behavioral facts. No filler.

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 no-parameter, no-output, single-purpose action, the description covers the action, side effects, and how to reverse it. Only the relationship to sibling power/display tools is left to inference.

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 takes no parameters at all, so there is nothing for the description to disambiguate; the baseline for a zero-parameter tool is 4.

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?

States a specific verb and resource ('Lock the screen') with an immediacy qualifier. The clause 'Apps keep running' implicitly distinguishes it from the nearby sleep_display/sleep_computer siblings, but neither is named, so the differentiation is suggestive rather than explicit.

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 is only implied: you lock the screen when you want to secure it. There is no explicit when-to-use versus the very similar siblings sleep_display and sleep_computer, and no when-not guidance, though 'Apps keep running' gestures at the distinction.

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