Hey there,
I don't think there's a criteria set on what type of sources you should annotate, and this is coming from someone who did a Major Work on history-based video games so majority of my sources were video games, blog posts written by academics and quotes from the game developer's tweets lol. When you're annotating a source, just make sure you can cover the following ideas:
- Why is this source relevant to your topic?
- How did this source help you develop your own ideas?
- Who is the composer of the source? Are they reliable and why?
- What is their agenda?
Majority of your annotation should be explaining why this source is important to your topic so make sure that you have a few dot points covering this before actually writing the annotation. Once you start writing, you'll find that 200 words isn't a lot
Hope this helps!
Edit: I'll also add that I did source annotations last (i.e. once I finished writing my essay) because I was able to judge which sources I found to be the most useful and did my annotations based on that.