Tiago Forte has done a few interviews with people in the tools for thought space, evaluating whether or not they are good for a Second Brain.
1. Searchability: The ability to quickly and reliably find the notes you need.
2. Duplication or Reusability: The ability to reuse past work.
3. Access: Access to a given note with minimal hassle.
4. Share: The ability to share and collaborate on your notes.
5. Ease of Use: Editability.
6. Upgrade: Learning path from beginner to advanced.
7. Transfer: Ability to move your notes to another app.
8. Connect: Linking ability.
9. Capture: Can capture a wide variety of formats (text, images, videos, pdfs, word documents, etc).
10. Organize: What tools to organize and shape the content you put there?
11. Security: How secure is your data?