The three lines
1. WHAT DONE LOOKS LIKE. Describe the finished state, not the steps. "Every enquiry from yesterday has a reply in drafts and is tagged by type." Not "read the inbox, then sort it, then write replies."
2. WHAT IT IS ALLOWED TO DECIDE ON ITS OWN. Be specific. "It can decide which category an enquiry belongs to and it can choose which template to start from."
3. WHAT IT HAS TO BRING BACK TO YOU FIRST. The line it never crosses. "It never sends. It never quotes a price. Anything mentioning a refund comes straight to me."
Those three lines ARE the instruction file. You have not written any code and you are already most of the way there. Paste them in as the brief and the build is mostly description from that point.
Pick the right job first
Do not start with the clever one. Pick the job you do every single week that you resent. Weekly and resented is the test. Something you do once a quarter is not worth a weekend, however annoying it is.
Three is the number, not thirty. One thing that runs on a schedule so you stop doing it at all. One file that tells it how your business works so you stop re-explaining yourself. One connection to where your work already lives so it can see the thing instead of you pasting it in. When those three run, the rest start to make sense on their own.