Is Rashi really saying that Ya’akov was guileless?
(25,27) “The lads grew and Eisav became a man who knows how to ensnare, a man of the field, and Ya’akov was איש תם (a guileless man) who dwelled in tents.”
Rashi explains here that someone who is not astute in deceitfulness is called תם - guileless, yet Rashi also explains that the posuk “Ya’akov told Rachel that he was her father’s brother” (29:12) means that Ya’akov told Rachel that if her father, Lavan, was going to be deceitful then he was also his brother (his equal) in deceitfulness!
But I heard that R. Tzvi Yaakov Klein explained that Ya’akov was very astute in the art of deceitfulness, as we see from his cunning in dealing with Eisav and Lavan. But his normal, preferred behaviour was simpleness and artlessness, and he only set this aside to use cunning and deceit according to the needs of the moment. Therefore he was called an איש תם, a man - a master - of guilelessness, controlling when to use the superior character trait of guilelessness and when to use cunning instead.
However, someone who is not astute in deceiving is called only תם - guileless, and not an איש תם. This is what Rashi is coming to explain - someone who is not astute in deceitfulness is called guileless, unlike Ya’akov who was a master of guilelessness.