Since January 2019, there is a plugin on the Jetbrains website called kdoc-generator.
https://plugins.jetbrains.com/plugin/10389-kdoc-generator
  Plugin to generate class and method KDoc.
This generator functions exactly like JavaDoc.
That means when you create a commentary with "/**" and press enter, the kdoc-generator creates automatically "@param" or "@return" tags for the parameter and return values of the method directly below this created commentary.
When you type /**
in your file above a method you wrote and then press enter you get something similar to this:
/**
 *
 * @param str 
 * @param age
 */
fun foo(str: String, age: Int) {
}
To install this Plugin directly in Android Studio:
- open File/Settings (Mac: AndroidStudio/Preferences)
 
- choose Plugins
 
- click Browse repositories...
 
- enter "kdoc-generator" in searchbar
 
- klick Install
 
- restart Android Studio
Now the kdoc-generator is installed and you can use it directly.
 
Additionally Jetbrains developed a documentation engine for Kotlin, that you can use to convert your documentation in Kotlin files to some standard formats, e.g. HTML
https://github.com/Kotlin/dokka
  Dokka is a documentation engine for Kotlin, performing the same function as javadoc for Java. Just like Kotlin itself, Dokka fully supports mixed-language Java/Kotlin projects. It understands standard Javadoc comments in Java files and KDoc comments in Kotlin files, and can generate documentation in multiple formats including standard Javadoc, HTML and Markdown.