The decision problems of Section B.3 of Transducers — equivalence and zeroness of weighted automata over the field of rationals — are about algorithms whose inputs are weighted automata. A weighted automaton over $\mathbb{Q}$ with states and letters in $\mathbb{N}$ is described by a finite code: its transitions $(p, u, (a, b), q)$, from $p$ to $q$, reading $u$, with weight $a / b$ given by an integer and a natural number, and its lists of initial and final states. A code is valid if the automaton it describes is a genuine weighted automaton, i.e. every input string has finitely many accepting runs; validity is the promise under which the decision procedures of Theorems B.3.3 and B.3.7 are correct.