[mzarate06]

I don't know about needing to be the "best", or an "expert", but I do believe a consultant should have a certain skill level, or set of skills, that provides some value to a team.

That's to say some consultants are very strong engineers, in the general sense; very capable in various roles. While others might possess a sufficient narrow skill set. E.g. maybe a front-end React dev, or data engineer assisting with integrating parts of a data pipeline, or a SQL consultant helping trouble shoot database performance issues. Other times, a team covers both bases (high degree of skill breadth, and depth), but lacks time to devote to all pressing issues.

So consultant relationships are formed for any number of reasons; they need not be an expert, necessarily.