Since the information at https://www.bluetooth.com/specifications/gatt/ is kind of hard to obtain. It only has links to pdf's and those pdfs does not have all information.
There are however xml-files available but I haven't found any links to them.
I have created this repository and wiki to make it more accessible.
16-bit UUID Numbers.json is a json-representation of the pdf that can be downloaded from https://btprodspecificationrefs.blob.core.windows.net/assigned-values/16-bit%20UUID%20Numbers%20Document.pdf
This document GATT Specification Supplement PDF Is actually what I was looking for. I don't where you are expected to find this link. I found it in a post on stackoverflow. The document contains data fields for characteristics.