We introduce a class of good endofunctors of \(C^{*}\) -algebras, endow it with a structure of a bimonoidal category, and define homotopies of natural transformations between such endofunctors. For every pair of \(C^{*}\) -algebras and a good endofunctor, we construct a commutative monoid of generalized morphisms, and endow these monoids with a bilinear composition. This construction generalizes the homotopy category of asymptotic homomorphisms used in the definition of the Connes–Higson E-theory. We also introduce the notion of asymptotically adjoint good endofunctors, which has interesting applications to E-theory and K-homology.
