Link custom apps with 1password

I couldn’t find a way to make custom apps use 1password to fill in credentials.
There’s actually quite a few apps available in the App Store that don’t offer to retrieve credentials from 1password (eg. AWS Console, Freebe, …).

How does 1password linking with apps work ?
Does it require something on your end ?
I was kind of expecting it to work with any login form, like it does with the browser extension…