What to prepare for a job interview that I'm going conduct

I work in a small company as CTO. I have been informed that I must conduct a job interview the very next day (the meeting is already setup). We have no clear definition of what is the role we want to fill and what kind person we are looking for. We even have no budget for what we can spend on hiring a new person.

The person attending the job interview is a previous colleague by another person that is somehow the "decision maker" in the company (that decision maker also have no clear definition of roles he have and have just been installed by one of the owners of the company, without any proper process - and they didn't even know each other or any mutual contact network when it happened)

I have requested to get at least a CV for the person I’m going interview - without getting it. In the interview it will be 3 people from our company:

• CEO
• CTO
• The "decision maker" without any defined roles

For me this kind of process seems so unbelievable unprofessional and I’m not even sure how I should behave in this situation. Recently it has been other instances like this one, where I just refused to attend the meeting. I’m considering to just attend the meeting without actively participating in it – or even if I should interview him for replacing me (as it is so much other mess in the company that makes me just want to leave).

• Am I being too judgemental of the process here?
• What should I do this situation?

You don't need a CV. You might need to know vaguely which relevant places this person has worked before, but you can ask that during the interview if you can't find it out from googling them. I prefer to ask questions that lead to answers like "while at XYZ I had to ABC and how that went was...." rather than just "where did you work?" so not knowing where they've worked is less of a hindrance than you seem to feel.

What you need to know is "what is the job?" (and it's quite likely part of the job is defining the job) and "why do one or two people in your company already feel this candidate can do it well?"

Here is what I would do. I would go to the person who asked me to attend the interview and ask

What are you looking for from me in this interview? Am I mainly there in case the candidate has questions for me, or do you want me to get us all some information, or just reassure myself this is someone I can work well with?

Those are likely the three possibilities of why you were included. A fourth is that they just think it would be awkward or rude to interview the person without you.

If your question about the purpose of the interview goes well and you get useful information from it, you could also add

Tell me a little more about [person] please. Why do you think they are a good fit? (Or, why are we interviewing them?) (Or, why are they coming in to meet us?)

This is strictly for your own comfort in trying to decide to what extent the decision is already made and how much input you genuinely have.

If you don't get a nice clean answer to the first question (what are you looking for from me), decide for yourself what your goal will be. I recommend finding out whether or not you can work with this person in this "we're just a little uwu smol company and can't have like job descriptions or cvs or anything traditional, don't oppress us we're changing the world" environment. Will they make it worse? Will them being on board make it easier for you to meet your goals, whatever their technical job description or title is?

Once you know that, you can contribute to the post-interview discussion. And if the person is hired, you can also make decisions about your own future, either staying and working with them or leaving them all to their own devices.