Modding etiquette questions

[Llama Feats]

I'm kind of new to modding, so apologies if this is a silly question. I don't want to mess anything up or make anyone upset. My question(s) is this:

Is it bad to make an addon of sorts to someone else's mod (extra items, hediffs, etc.)? What if I credit them in the mod and description - is it best to state that they can ask me to add it to their mod if they would like? Is it wrong to link to someone else's Patreon/Ko-Fi to credit them? What if they don't have anything on the mod page about using or adding on to the mod (and other people have)? If I need to ask, how can I contact them - what is the best way?

I have thought of plenty of mod ideas today, and some of them are addons, but I want to start working on an addon. I add a credit section on all of my mods.

EDIT: I read that it was okay, but I just want to make sure.

[Llama Feats]

For clarification, by "add-ons", I mean items and hediffs that use their defs (items, hediffs, custom defs, etc.), given that the person has the required mod installed.

As a bit of an example, let's say that I made a thought def and another hediff that needs one of their hediffs to work.

What if I add a patch that adds compatibility and features from their mod (and others) - should I still ask?

[Canute]

You allways should check what licence they use for their mod, and what these licence allow.
If you don't know just ask the author about it.

[Shinzy]

add-ons like this are totally fine!
It's just very considerate to let the author know your addon exists

[Llama Feats]

Thanks for responding, you two . I asked them, and they said yes.