Set hub variable

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

The description discloses that the tool is admin-route and firmware-sensitive (a meaningful caveat), and that it triggers Rule Machine subscriptions on the target variable. Annotations declare readOnlyHint=false, destructiveHint=false, and idempotentHint=true, which are all consistent with the description. It adds behavioral context about side effects (rule triggering) beyond the annotations, though it doesn't fully explain firmware sensitivity implications.

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?

Extremely concise: one purpose statement, one caveat, one when-to-use line, and one when-not-to-use line with an alternative. Every sentence earns its place with zero filler or redundant content.

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 description is well-complemented by a 100% schema coverage and an output schema existing. For a 2-parameter write operation with good annotations and full parameter documentation, the description adds the critical behavioral nuances (admin route, firmware-sensitive, Rule Machine side effects). It could be slightly more complete by elaborating on what firmware-sensitivity means practically, but for the complexity level, it's adequate.

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 100% (both name and value have descriptions in the schema), so the baseline is 3. The description does not add semantic detail about the parameters beyond what the schema provides. It doesn't explain what format 'value' expects or whether 'name' needs to be exactly as configured. At baseline 3 since schema fully covers 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?

The description uses a specific verb+resource ('Write a Hubitat hub variable') and adds a scope/characteristic ('admin route; firmware-sensitive'). It clearly distinguishes itself from siblings by noting it triggers Rule Machine subscriptions, versus hubitat_send_command for device commands. This is a strong purpose statement.

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 gives explicit when-to-use ('automating Rule Machine without a virtual switch') and explicit when-not-to-use ('sending a device command') with a named alternative (hubitat_send_command). This is exemplary usage guidance that differentiates from siblings.

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