night_mode

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

With no annotations, the description fully discloses behavior: it turns on lights via two sub-commands, does not affect speed/direction/power/clock, and is visual-only. No contradictions.

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?

Well-structured with clear sections: main action, usage hints, exclusions, inverse, return value. Slightly verbose but every sentence adds value; could be tightened.

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?

Fully explains the composite action, what it changes and doesn't change, and describes the return shape despite no output schema. Adequate for a zero-parameter tool with clear behavioral context.

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?

No parameters exist, so schema coverage is 100%, meeting baseline. The description adds context by explaining the tool as a composite of set_layout_lights and set_all_locos_lights, giving semantic meaning to the lack of parameters.

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?

Clearly states it sets layout to night mode by turning on all layout lights and locomotive lights, distinguishes from power/status commands, and names inverse (day_mode). Explicitly specifies it does not affect speed, direction, power, or signals, differentiating it from sibling tools like set_power, set_speed, and set_signal.

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?

Provides natural language examples ('put the layout in night mode'), states it's for demonstration-style lighting scenes, and explicitly lists what it does NOT do (track power, signals, etc.), guiding the agent on when to use and when to avoid.

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