Script code that talks to systems directly: files, APIs, databases
RPA bot software that uses the screens like a person: clicks, copies, types
AI agent a language model with tools: reads anything, drafts, explains
01/ 09
Three kinds of helper
A script is code that talks to systems directly: it reads files, calls an API, writes to a database. Fast and exact, but only for inputs it was written for.
An RPA bot (robotic process automation) uses the screens the way a person does: it clicks, copies and types, following steps someone recorded. An AI agent is a language model with tools: it can read messy input and decide what to do, and it can be wrong.
02/ 09
The job: five invoices
An example business gets five supplier invoices this morning, and each one has to go into the accounts app.
Three are routine. One comes from a new supplier with a different layout. One is a phone photo of a paper bill, and its numbers don't add up.
03/ 09
Way 1: a script
The script reads the data export and the two PDFs in the usual layout, and posts them through the accounts app's API in about a second.
The new layout and the photo stop it, and it says so. A loud stop is a good failure: nothing wrong got in.
04/ 09
Way 2: a bot that uses the screens
The bot needs no API: it opens each invoice and copies from the spot where the total usually is. Useful when the only way into a system is its screens.
Watch invoice 4. The new layout has a different number in that spot, and the bot types it in without a word. A quiet wrong answer is the worst kind.
05/ 09
Then the screen changes
The accounts app ships an update and moves its Save button. The bot's recorded clicks now point at nothing, and every invoice gets stuck.
The script and the agent don't notice: they talk to the app through its API, which didn't change.
06/ 09
Way 3: an AI agent
The agent reads all five, including the new layout and the photo. It notices that the photo's items add to ₹1,890 while the total says ₹1,980, and asks.
It is slower than the script, it costs something per use, and it can misread. So it drafts each entry and a person approves it.
07/ 09
Side by side
The script: fastest and exact, but strict. The bot: works without an API, but brittle when screens change, and it can be quietly wrong. The agent: handles the messy ones, but needs a person's yes.
08/ 09
Which one do you need?
Answer six questions about your own job on the stage. It starts with the answers for this invoice job.
The chooser is a rule of thumb, not a verdict. The habit behind it is to try the simplest thing that works first, and add an AI model only where a step needs reading or judgement.
09/ 09
Most real jobs are a mix
The best answer to the invoice job uses all three ideas: a script takes the regular invoices, an agent reads the odd ones, and a person approves the agent's drafts. The script does the plumbing; the agent does the reading; the person keeps the yes.
Every post, stop and approval leaves a receipt, so you can see later what happened to each invoice.