That's true; inside `hello_i_accept_pointers` there's no syntax at callsites to indicate that a mutable pointer is being passed. However, the variable being passed is of pointer type, which is readily apparent from the context of the function - the pointer parameter is declared in the same file, likely only lines above the callsite in question. This is still better than having to find the declaration of the called function, which is probably in a different file altogether.