Straightforward and truthful talk might be described with the adjective candid. If you're always candid, your parents will know that they can trust you.
A serious-minded politician might suggest engaging in a "candid discussion" about a complicated topic like health care or the environment, because candid means "open" or "frank." Remember that TV show Candid Camera? It was called that because its hidden cameras supposedly showed a candid view of reality. In photography, candid has become a noun meaning "an unposed photo." The word comes from Latin candidus, meaning "white," which was later extended to mean "pure." Candid talk provides the pure, unvarnished truth.
Definitions of candid
openly straightforward and direct without reserve or secretiveness