# Unknown Vector Valued Function

I am trying to evaluate this: D[f[x[t, k, l], t, k, l], k, l]

where x[t,k,l] is a 2x1 vector and the output of f is 2x1 as well. Currently the function just outputs it as if it were a scalar quantity. How do I form my assumptions (if I need them) or what do I specify such that it works in the intended way?