In this paper, we investigate a way to promote the reuse of legacy tools (or transformations) in specic contexts (defined by specific metamodels). More precisely we suggest a model transformation approach to achieve this purpose. We first introduce a language based on a metamodel called Modif in order to specify the differences between two semantically close metamodels. We can generate automatically data migration components from a Modif specification. They enable to put data complying with the specific context under the scope of the legacy tool. But more importantly in the case of a rewriting tool, they enable to put the tool's outcome back into the original specific context. Then we propose a process and a set of helpers based on Modif to automate the reuse of legacy tools for domain specific contexts. To illustrate this approach, we apply it to the case of simple finite state machines.