Create environment or config variables for Balena fleets, devices, or services. Use to set named values, including secrets, without exposing them in chat.
Create a named environment or config variable. Values may contain secrets; do not repeat them in chat.
| Name | Required | Description | Default |
|---|---|---|---|
| kind | Yes | ||
| name | Yes | ||
| value | Yes | ||
| owner_id | Yes |
Changes observed during successful MCP inspections.
v0.3.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate this is a non-read, non-idempotent operation. The description adds a useful behavioral note: values may contain secrets and should not be repeated in chat. However, it does not disclose other relevant behaviors like duplicate handling, ownership requirements, or what a successful creation returns.
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 extremely concise: the first sentence names the action and object, and the second delivers a critical security instruction. No 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?
For a mutation tool with four required parameters, no output schema, and zero parameter documentation in the schema, this description is too thin. It omits what the kind values mean, how owner_id should be determined, conflict/duplicate behavior, and expected results.
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 description coverage is 0%, so the description must compensate, but it only adds meaning for the 'value' parameter by warning about secrets. It provides no semantic guidance for 'kind', 'owner_id', or 'name', leaving most parameters opaque.
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 states a clear verb ('Create') and resource ('environment or config variable'), distinguishing it from sibling update/delete/list variable tools. It is not fully specific about the different kinds/scopes, but the overall purpose is identifiable.
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?
No guidance is given on when to use this tool versus balena_update_variable or balena_delete_variable, nor does it explain which kind to choose for which scenario. There is no mention of prerequisites such as owner_id resolution or uniqueness constraints.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.