Why evals, and their vocabulary

You ship a small prompt change to the pre-contract enquiries agent: "be more concise". The freehold enquiries look tidier. Two weeks later a solicitor notices that, on leasehold files, the agent has stopped asking about service charge arrears, because the shorter drafts dropped the paragraph that mentioned the management pack. Nothing crashed and no test failed. The change was judged on a handful of examples someone read on a Friday afternoon. An eval exists to make that kind of regression visible on the day you make the change, not two weeks later on a live file.