What is the most important criterion for choosing a secondary antibody?

Considering the host and target species is the most important criterion for choosing a secondary antibody. The host species refers to the animal in which the secondary antibody was generated. It is crucial that the species used to generate the secondary antibody is different from the host and target species of the primary antibody. For example, if a primary antibody was derived from a goat, then you must choose an anti-goat secondary antibody that was generated in a species other than a goat.