When providing services in multi-administrative multi-domain networks, domains usually disclose a topology aggregation composed of a set of abstract links connecting their border nodes. Such an aggregation is motivated by the will of limiting the information exposed to other domains. This, however, leads to inefficient resource usage. In order to enable effective collaborations between domains, in this paper, we propose to enrich the topology aggregation exposed by domains by promoting the inclusion of abstracted non-border network nodes and the network slices supported by each domain. Our evaluations on real and random topologies show the significant potential gains in terms of admission ratios and resource usage that such additions bring.