List virtual devices

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered. The description adds useful context about Rule Machine having no API and the mechanism for triggering rules, which adds value beyond annotations. However, it doesn't describe the output structure or whether results include hub variables as well as switches, which would add further transparency value.

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 at roughly 40 words, split into a purpose statement and a compact use/when-not-to-use block. Every sentence earns its place with zero filler or redundancy.

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?

With readOnly/idempotent annotations, simple params, and an output schema present, the tool doesn't need extensive documentation. The description addresses purpose, usage context, and sibling differentiation well. Minor gap: it doesn't clarify whether hub variables are also returned by this tool or only by get_hub_variable, but this is a modest omission given the overall completeness.

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 coverage is 33% — only 'query' has a description ('Optional filter'). The description itself doesn't elaborate on parameter semantics beyond what the schema provides. With low coverage, the description could do more to clarify param formats, but the params are simple (limit, query, offset) and largely self-explanatory by schema definition alone. Baseline 3 is appropriate.

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 verb+resource ('List devices that look like virtual switches/buttons') and explicitly distinguishes from the sibling tool hubitat_list_devices by noting this is for virtual devices/Rule Machine levers, not physical devices. The purpose is specific and unambiguous.

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 explicitly states when to use ('finding a virtual switch to drive Rule Machine') and when NOT to use ('controlling physical devices (use hubitat_list_devices)'), naming the exact alternative tool. This is exemplary usage guidance with explicit exclusions and an alternative named.

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