How to push assets (images) and metadata to Algolia Search from Contentful

We are having an issue with Algolia Search. Basically we can not get the media url from Algolia and Metadata Tags (general tags) are also not getting back the data in Algolia, it only get use the ID which is not useful. Title and Description works perfectly fine, at the end of the day it just the text so I do not see the problem with that.
Here is the payload that we use:

{
"title": "{ /payload/fields/heading/en-US}",
"description": "{ /payload/fields/shortDescription/en-US}",
"slug": "{ /payload/fields/slug/en-US}",
"imageId": "{ /payload/fields/mainImage/en-US}",
"metadata": "{ /payload/metadata/tags}"
}

Basically we need the URL from media inside the Algolia, but the way we have set up the payload, it will not work