I think it is not really a "script"; it is a description of the character. This will affect as you will do in the game, and you will have to make it up what happens according to the circumstances as it is being done, instead of everything being written ahead of time. (Even if you do have plans, which you might (I often will, and the GM also often will), things will happen unexpectedly and cannot use the plans exactly like they are anyways.)
I think that you do not generally need game mechanical traits in your character sheet to do this; you can write it in a spare section if you want to do (it is useful to have spare sections for this and other purposes; I will often want to add many extra notes that there are not pre-defined sections for).
In GURPS, you would generally represent some of such things with mental disadvantages and quirks. I prefer to not use mental disadvantages unless I specifically want the game effects of those disadvantages (e.g. if you are unlucky, or cursed, or take only half as many turns as other characters, or you will tell the truth half of the time that you do not intend to do so, etc), and would generally rather have a choice, even if my character's personality is supposed to be something, I can do it by myself instead of making the game to try to do it for me. I do usually add quirks though, and I do more often want physical and social disadvantages.
I think that you do not generally need game mechanical traits in your character sheet to do this; you can write it in a spare section if you want to do (it is useful to have spare sections for this and other purposes; I will often want to add many extra notes that there are not pre-defined sections for).
In GURPS, you would generally represent some of such things with mental disadvantages and quirks. I prefer to not use mental disadvantages unless I specifically want the game effects of those disadvantages (e.g. if you are unlucky, or cursed, or take only half as many turns as other characters, or you will tell the truth half of the time that you do not intend to do so, etc), and would generally rather have a choice, even if my character's personality is supposed to be something, I can do it by myself instead of making the game to try to do it for me. I do usually add quirks though, and I do more often want physical and social disadvantages.