“Jack of all trades, master of none” is a figure of speech used in reference to a person that is competent with many skills, but no particular one. An alternate phrasing says “Jack of all trades, master of none is oftentimes better than master of one.”
The earliest recorded versions of the phrase do not contain the second clause. Indeed, they are broadly positive in tone. Such a Jack of all trades may be a master of integration, as such an individual knows enough from many learned trades and skills to be able to bring the individual’s disciplines together in a practical manner. This person is a generalist rather than a specialist.
He’s a so-called jack of all trades and master of none.