Torbjorn,

This is how searching with the API works: 

If you're an agent logged into the portal, you can pull up solution articles, tickets, notes and posts with a certain keyword using a query like this - search/home?search_key=tag. 

However, an end user can pull up solution articles with a query like this: support/search/solutions?term=tag.

If the search string is a part of the solution title or is present in the body, the solution also gets pulled up. I hope this helps :) 

Yes, but this is not well-formed data. How do I get this in xml- or json-data?

Ok, just found out that I can search with the following url: /search/home/solutions.xml?search_key=tag

However I haven't found a way to search solution articles, no matter of folder or category, on their tags. Specifically articles with a certain tag; I'm not interested in them if the title or body contains the tag.

I'm sorry but you can't pull up solution articles just based on their tags. You can't filter solutions based on just titles, descriptions or tags. 

Hello,

The ability to search and fetch articles via API is now available. Please refer to the documentation below for syntax and response codes.

https://developer.freshdesk.com/api/#solution_article_attributes

Cheers!