A message transformation selection tool and method for use in a distributed message processing system running applications on subsystems using incompatible message formats, selects the most appropriate output message format for a given input message format. Firstly, the tool determines compatibility of each field of the input message format with fields of all possible output message formats. Next, it statistically analyses the values of message fields in messages stored in message logs for each of the subsystems. On the basis of this analysis, the tool selects the best fit output message into which to transform a given input message.