Personality tests are a common tool in the Life Coaching industry but I don't use them and here are some of the reasons why.
Firstly, they can be expensive. They can cost hundreds and even thousands of dollars (and you can bet the coach is taking a cut of that). There is something unseemly about coaches selling clients personality tests as a starting point for working with them.
Secondly, personality tests are often also used as a substitute for the coach helping the client to know themselves better. Learning to understand ourselves is a process and a test simply telling you what kind of personality you have means you will miss out on all the vital self-knowledge the process provides. Personality tests can help inform how you are, but they cannot reveal who you are.
Thirdly, everyone who takes a personality test always has the same reaction. They go through their results and say they "agree with this part" or "disagree with that part". In other words, they already know themselves (even if they cannot articulate it); they must do or they wouldn't be able to agree or disagree.
Fourthly, psychology is not a hard science; it cannot determine definitive truth. However, it does like to dress up as a one by using lots of data to quantify its findings. Personality tests can create the illusion that the findings are facts (when they are really just insights) and can thus be given undue weight in the coaching process.
Finally, personality tests essentially put you in another box. Do you really want to be in another box? Society has already boxed you by race, religion, culture, age, nationality, gender, sexual orientation and class. Maybe some of your problems are a direct result of this social boxing. Maybe it's time to step outside of some boxes rather than into another one.
Personality tests are not worthless. They can be useful when understood and applied properly but they are just one of many tools. So my advice is save your money, especially if you are at the start of your coaching journey. There are better ways.
