Some of the specialty tools that you might need for most of your appliance repair include a nut driver set, multimeter, and screwdriver set. Basically, it is not possible to decide on the tools one might need while working on a specific appliance.
Therefore, the technicians often go for a casual visit to the site with only a few tools for an inspection. If the problem seems solvable with just those tools, then they might just get over with the job on an inspection visit itself.
But if the problem seems unidentifiable, then the technicians will go back to the site on another date with all the tools and necessities.