When a mixin does not define any parameter, parentheses are optional and should not be added to improve code readability.

Noncompliant Code Example

@mixin my-mixin() {   /* Noncompliant */
  ...
}

@include my-mixin();  /* Noncompliant */

Compliant Solution

@mixin my-mixin {
  ...
}

@include my-mixin;