I noticed something else (I found a workaround) which is "caused" by the URL-UTF-8 encoding.
API fails when using complex search (multiple parameters on the placeholder %s). That's because URL-UTF-8 encodes the ampersand character (&).
I replaced encoding with UTF-8 and complex search is back to life again.
Please consider some websript suggestions (in this new topic).
Please strogly consider point 4. I just realized we will lose "Advanced scripting" tricks by using json.
Using "traditional" scripting we were collecting information on the selected API stream (use regexp, etc) and storing it to temporary tags, e.g. scan all tracks to find total number of discs to make it available to all tracks (in a new tracks loop).