> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rigbox.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Validated parameters

> Expose bounded application settings with defaults and validation.

## Declare a parameter

```yaml theme={null}
params:
  - key: mode
    type: select
    label: Runtime mode
    default: production
    required: true
    envVar: APP_MODE
    options:
      - { value: production, label: Production }
      - { value: staging, label: Staging }
```

Parameters describe user choices, not secrets. The app receives `PARAM_MODE` and the explicit `APP_MODE` mapping. For incremental release preparation, missing required values, values outside declared options, invalid validation patterns, and invalid environment names fail validation.

## Use the setting

Read the mapped variable from your application and deploy from the local manifest directory. Explicit app environment values can override parameter-derived variables, so avoid declaring a conflicting `env.APP_MODE` unless intentional.

After deployment, inspect the app's parameter settings with `rig app param ls --app <APP_NAME>` and verify the application uses the selected behavior. Recipe-backed apps can expose parameter controls and reconfiguration hooks; consult [catalog apps](/guides/catalog) for that flow.

Do not rely on a parameter label or type alone to enforce a security boundary. Validate inputs in the application too. The [configuration reference](/reference/rig-yaml/configuration) describes the field relationships.