createVarCreate environment variables or credentials by specifying workspace, app, environment, and key-value data. Use it to manage configuration and secrets across development, preview, and production.
Create a new environment variable or credential
| Name | Required | Description | Default |
|---|---|---|---|
| env | No | ||
| region | No | ||
| appSlug | Yes | ||
| requestBody | No | The JSON request body. | |
| workspaceSlug | Yes |
Changes observed during successful MCP inspections.
v0.5.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false and destructiveHint=true, indicating a mutating operation with potential side effects. The description adds no extra behavioral context, such as overwriting behavior, permission requirements, or impact on existing variables, so it fails to add value beyond the annotations.
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 a single, concise sentence with no redundancy, but it is under-specified. It is not verbose, yet it also does not provide enough substance to be considered well-structured for the tool's complexity. It earns a middle score for being appropriately short but lacking informational depth.
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 tool with 5 parameters, a nested requestBody, no output schema, and low schema coverage, the description is very incomplete. It does not mention required fields, the requestBody structure, possible values for env, or any operational side effects, leaving the agent with insufficient context to call the tool correctly.
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?
With schema description coverage at only 20% (only the requestBody field has a description), the description does not compensate for the undocumented parameters. It does not explain env, region, appSlug, or workspaceSlug, nor does it elaborate on the requestBody structure beyond what the schema provides. The description adds zero parameter meaning.
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 a specific action (create) and resource (environment variable or credential), which distinguishes it from sibling tools like updateVar, deleteVar, and listVars. However, it does not mention the workspace/app scope or differentiate from similar creation tools like createToken, so it is clear but not fully differentiated.
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 no guidance on when to use this tool versus alternatives, such as importVars for bulk creation or updateVar for modifying existing variables. It simply states the action without any contextual use cases or exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.