Stop Chatting With Spreadsheets — Francesco Galletta & Felippe Felisola Caso, Monzo

Fast answers are easy to get. Answers you can trust with your money are harder. Francesco Galletta and Felippe Felisola Caso build a financial-analyst agent harness live, using one real problem: paying for a wedding. They show the five design principles they use for AI you can trust: shared domain, consistency, evidence, accountability and verification. They also explain why calculations belong in code instead of in the model's head. Note: the speakers work at Monzo but are not presenting on Monzo's behalf. 🎟️ Join us at the next one: AIE CODE Summit → https://aie.codes Speakers Francesco Galletta — LinkedIn: https://www.linkedin.com/in/francescogalletta/ Felippe Felisola Caso — LinkedIn: https://www.linkedin.com/in/felippecaso/ Monzo — https://monzo.com Timestamps 0:00 Intro: Francesco & Felippe 2:54 Using AI for impact, not token-maxing 4:22 Speed isn't the bottleneck. Trust is. 7:25 Components vs. design principles 8:45 The 5 principles of trust 12:13 The use case: budgeting a wedding 17:05 How the principles build on each other 20:40 Principle 1: Shared domain 25:59 Live demo: planning with the agent 30:42 From plan to decision tree 35:48 Why long linear chats fall apart 36:48 Principle 2: Consistency (math belongs in code) 55:50 Principle 3: Evidence (show the receipts) 1:00:17 The "master file" horror story 1:06:42 Principle 4: Accountability 1:20:39 Principle 5: Verification 1:24:16 Golden examples & outside reference points 1:34:05 Q&A: How many harnesses should you build? 1:38:11 Don't over-sharpen the axe 1:44:00 Q&A: Skills vs. a dedicated harness 1:48:31 Takeaway: design for trust on purpose