When do you say direct and indirect?

Hereunder several example of the employ of "direct" as an adjective:

direct consequence, direct descendant, direct action, direct discourse or speech (British), direct evidence, direct cost.

You can also use it to mean: frank, open, sincere; a direct answer, a direct way of doing things.

"Direct" as an adverb: I shall write to you direct, the train goes direct to Boston .

Several examples of the employ of "indirect" as an adjective:

an indirect route, to make an indirect reference, to answer a question in an indirect way, indirect cost, indirect object, indirect discourse or speech (British).