From mobile apps to microservices, from small startups to big enterprises, Gradle helps teams build, automate and deliver better software, faster.

Gradle Community

The bad but quick way would be to just add the artifact manually to the publication.

The better and proper way is to define a feature variant with according attributes.

Basically what `withJavadocJar()` does for a standard Java project. You can probably have a look there.

Is there anything standardized there? Or is it just OK to co-opt the Javadoc variant?

Dunno what you mean by co-opt.
But well, as what you generate is a JavaDoc jar, I would set up the feature variant exactly like `withJavadocJar()` does it.
Make  a simple Java project with that and have a look at the output of the task  `outgoingVariants` to see how it should look like in the end,
and also at the published Gradle Module Metadata file with such a variant.