Please register to tpp.hikvision.com, you will be provided with NDA form to sign , and all the documentation will become available to you.

The documentation you download there will contain wattermark with your company name. If you share it and they find out, they can pursue legal actions.

Hence why you cannot see a lot of documentation in public. If any its on random forums.

Since your device is web based, you can always use Developer tools and see endpoints and all the CRUD that devices does.