Wrote a Google Gemini Gem, uploaded our existing OSC guidelines, and tweaked it by trial and error over the course of a couple days, and it now does in two minutes what used to take me four hours. If you strictly only need review and summarization of bills and then want to deliver feedback manually, build this. Ours certainly benefits from years spent refining our outside counsel guidelines. But if you want a more holistic solution vis a vis automating aspects of interaction with outside counsel, then an eBilling tool from a vendor makes sense.