How do you calculate First Order Condition? Manually? Can any package do this?Maybe Mathematica? lol.

FOC are calculated by the Dynare preprocessor, which is a C++ program computing analytical derivatives of the model equations.

Actually, Dynare does not compute the FOCs (like e.g. the Euler equation). Dynare does the linearization of the FOCs by automatically computing the Taylor approximation, i.e. taking the required derivatives.

Thanks for correcting me.

Note that there is however one case where Dynare really computes the FOC: it is when using ramsey_policy.