Below is the full configuration available with defaults values:

"example" => [
    "type"   => "anomaly.field_type.textarea",
    "config" => [
        "rows"          => 6,
        "min"           => null,
        "max"           => null,
        "show_counter"  => false,
        "default_value" => null,
        "show_counter"  => true,
        "autogrow"      => true,
        "storage"       => null,
Key Example Description
rows 7 The number of rows high the textarea should be.
min 100 The minimum length of text allowed.
max 250 The maximum length of text allowed.
show_counter true Define whether to show the character length counter or not. If `max` is defined the counter will show characters remaining.
autogrow true Define whether to automatically adjust height past the input rows while typing.
default_value Some Example Text The default value.
storage null Can be either `null`, `json` or `serialize`.