Specialized tools are not a good analogy for what it’s like to be a specialized expert.
I just bought a super-specialized tool:
It’s a plier to manipulate a small retaining ring that can only be turned by inserting pins in these two little tiny 1mm holes in the ring.
I’ll probably use this tool twice in my life.
It’s a very specialized tool. I bought it to help me with only one job. It (hopefully) does that job very well, but there are only a very narrow range of jobs this retaining ring plier is suited to, and that list of jobs is unlikely to change over time.
This reminds me of a somewhat tangential story. A college friend’s father was a senior airplane mechanic. When he was conducting job interviews with junior mechanics, he would ask to see their toolbox. If they had more than zero pairs of pliers, he wouldn’t hire them. That’s apparently because with airplanes, there’s always a more specialized tool for the job that will more precisely fit the intended application. Pliers are a compromise compared to an exactly-fitting wrench, for example. The imprecision of a compromise tool is dangerous when we’re talking about airplanes and people’s lives.
Anyway, specialized tools are not a good analogy for specialized experts.
As an expert, you can change and grow. Your relationship with clients may lead you to new, complementary additions to your expertise.
If the idea of specialization is off-putting to you because it implies inflexibility, don’t worry. Specialization addresses marketing inefficiencies and makes it possible for you to cultivate economically valuable expertise, but it doesn’t lock you into a highly narrow range of functions for all of time.