A Man Who Still Googles "EORI Number" Explains Agents and LLMs

I have been working in indirect tax for the guts of 20 years, and I still google "EORI number" every 6 weeks or so, just to make sure it means what I think it means. It does. It has meant the same thing the entire time. This is, broadly, the level of technical confidence I bring to AI as well. So in the spirit of solidarity with everyone else nodding along in meetings pretending they know what an "agent" is, here's my attempt to explain it properly. LLM (Large Language Model) Think Claude or ChatGPT: software trained on enormous amounts of text that's gotten very good at predicting what word should come next, to the point where it can hold a conversation, draft a memo, or explain VAT grouping rules without falling over. In a tax context, you ask it "does reverse charge apply to this supply?" and it gives you a plausible, well-structured, confident answer. It is not a tax adviser. It is extremely good at sounding like one. Its like your buddy who's read a lot. Brilliant for a strong opinion delivered with total conviction. You would not let him file your tax return. You would, however, let him name U2s first 5 number one records. If you want to actually start using one, here's the easy entry point: next time you've built a presentation, paste the content into Claude or ChatGPT and ask it to review it as if it were a sceptical senior stakeholder. You'll get back questions you hadn't thought of, for free, before anyone in the real meeting gets the chance to ask them. API (Application Programming Interface) This one's simpler than it sounds: a defined way for one piece of software to ask another piece of software for something, and get a sensible answer back. Your checkout system needs to ask the EU's VIES database "is this VAT number real?" The API is the agreed format for asking that question and getting "yes" or "no" back, the same kind of handshake that lets your accounting software talk to Stripe, or your calendar talk to Zoom, without anyone hand-building the connection each time. It's a bit like ordering a pint. You don't go behind the bar and pull it yourself, you say the words "pint of stout, please" in the agreed format, and the barman, who has no idea what's going on in your head otherwise, hands you exactly what you asked for. Different pub, same words, same result. That's an API. You probably won't build one yourself, but it's worth knowing when you're being sold one. If a vendor says their system "integrates" with yours, ask what API it uses, it's the difference between a real, maintained connection and someone manually exporting a spreadsheet every month and calling it integration. Agent An agent is software that doesn't just answer one question, but is given a goal and goes off and does several things, in some order it decides itself, to get there. Instead of you manually checking a customer's VAT number, then checking their billing address, then checking if reverse charge applies, then drafting the invoice note, you tell an agent "make sure this sale is VAT-correct," and it works through all four steps itself, in whatever order makes sense, and tells you when it's done. It's a bit like asking your other half to go to the shop and "get stuff for the dinner" instead of a list. A huge act of trust. Sometimes they comes back with a perfect dinner. Sometimes they come back with garlic bread and a bottle of orange and a bag of sugar and a strong sense that the original goal has been quietly redefined along the way. The agent decided the steps. You just live with the outcome. To actually start using this, give it a goal, not a single instruction, and see what it does with it. Instead of "summarise this contract," try "review this contract and flag anything that looks unusual for a standard supply agreement." Same effort from you, more done on the other end. Hopefully you found this helpful. Colm