How to add an array of tags with firebase mailchimp extension

Question

We have a collection of users, each with an array of skills. Each skill has a title and description. We would like those skill titles to be mailchimp Tags.

In the firebase extension setup, we have the Member Tags Watch Path set to "users", and the Member Tags Config as:

{
  "memberTags": [{ "documentPath": "skills[*].title" }],
  "subscriberEmail": "email"
}

We're following the instructions here https://extensions.dev/extensions/mailchimp/mailchimp-firebase-sync

And getting the error log: A property named 'memberTags' is required

We clearly have memberTags as the first property... any idea what we are doing wrong?

Thanks!