Generally, the harder it is to explain to someone you've just met at a cocktail party what it is you do on a day to day basis, the more interesting the work you're engaged in.
Arnold Kling applies a related rule of thumb to job security:
A job seeker is looking for… a well-defined job. But the trend seems to be that if a job can be defined, it can be automated or outsourced.
The marginal product of people who need well-defined jobs is declining. The marginal product of people who can thrive in less structured environments is increasing.
In other words, how easy is it to outline exactly what you must do day to day at work? The easier this task, the more at risk it is to being offshored or automated.