I think that a good philosopher needs at minimum:
* The ability to observe
* The ability to reason
* Some sense of what the important questions are
* Some felicity with language

My justification is as follows:
* If you can’t observe then you can’t validate or support your arguments
* If you can’t reason then your arguments will be flawed
* If you don’t know what the important questions are then your arguments may be valid, but nobody will heed them
* If you don’t have some felicity with language then your meaning will be murky, and people will get bored

On the other hand, if you have all these facilities then you’ll
know what to think about; be able to take guidance from what you see; be able to explore and form coherent arguments; and be able to articulate them interestingly and capably for yourself and others.

Moreover, we can tell good philosophy from bad philosophy by comparing the philosopher’s observations with our own; tracing through their reasoning; considering the impact of the question; and reflecting on how well the philosopher has articulated the material

Our ability to judge the quality of philosophy therefore depends on our own abilities to observe, argue, question and communicate. When we can do these things well, the credentials of the philosopher won’t matter so much. If we’re poor at these things then *who* may be more important to us than what and how and why.