I already had a working expense tracker built with React, Express and SQLite. For this task I had to pick an AI feature that actually made sense for it, not just bolt something on for the sake of it. So I went with a chat feature where you can ask questions about your own spending in plain English, like "how much did I spend on food this month" or "what's my biggest category", and it answers based on your real data.
Why this feature
The app already had a summary section showing totals and category breakdowns, but that only tells you so much. If you want anything more specific, like comparing two categories or checking a particular time period, you'd have to scroll through the list and do the math yourself. A chat feature solves that. You just ask the question and get an answer. It felt like the most natural extension of data I already had sitting in the database, and it's also the feature that actually forced me to think hard about prompts and streaming instead of just calling an API once and printing the result.
I did consider two other options first. Auto categorizing expenses as you type felt too small, more of a classifier than an AI feature. A one shot spending summary was decent but static, you'd generate it once and that's it. Chat felt like the one that actually used the AI SDK the way it's meant to be used.
