I have seen the effect of tools building in several contexts. The most successful were teams that respected the process in that they each, could and would build tools themselves and would adopt other's tools.<p>Without the symmetry then the creators has to make sure to keep up the pace on the global progress or be label as distracted by the tool creation.<p>Worst case the tool creators get separated from the main production and have to maintain the core groups utilities (which will become any code they don't want to maintain).<p>Tools have to be short to build, widely useful, and placed in a repository that is collectively maintained.<p>Remember the context that created the need for the tool may move on and the existing tools will have to be upgraded. The group should have a plan how to handle that.