set_variableUpdate a Homey logic variable to a new value. Ensure the value type matches the variable's defined type (boolean, number, or string).
Set the value of a logic variable. The value type must match the variable type (boolean, number, or string).
| Name | Required | Description | Default |
|---|---|---|---|
| id | Yes | Variable ID | |
| value | Yes | New value (must match variable type) |
Changes observed during successful MCP inspections.
v2.1.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false and idempotentHint=true, so the write and idempotent nature is disclosed. The description adds the type-matching constraint, but this is also present in the schema property description ('must match variable type'). No additional behavioral context (e.g., error handling, permissions) is provided, which is acceptable for a simple setter but does not exceed baseline.
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 two short sentences, front-loaded with the action, and contains no filler. Every word contributes to understanding the tool's core purpose and constraint.
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 two-parameter tool with no output schema and strong annotations, the description is adequate. It covers the purpose and the key type constraint. A minor gap is not stating behavior if the variable does not exist or the type mismatch handling, but this does not significantly hinder use.
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%, with both parameters described ('Variable ID' and 'New value (must match variable type)'). The description repeats the type constraint and lists allowed types, but adds no new meaning beyond what the schema already provides. 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 action ('Set') and the resource ('logic variable'), which is specific and unambiguous. It distinguishes from siblings by focusing on variable mutation, while list_variables is the only related sibling and covers reading, not writing.
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 provides clear context: use when you need to set the value of a logic variable. There are no exclusions or alternatives mentioned, but the tool's purpose is self-evident given the name and sibling set, so no when-not guidance is necessary.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.