An API in an analogy
Think of a bank teller's window. You don't walk into the vault to get your money: you go to the window, ask for what you need with a clear form and they hand it to you. An API is that window between two systems. One system asks the other for something in a defined way, for example "give me the stock for this product" or "create this order", and gets a structured answer, without a person copying and pasting data in between.
The acronym stands for Application Programming Interface. Behind the intimidating name there's something simple: a set of rules for asking for and delivering information between programs. It isn't a place you walk into by hand; it's the agreement on how things are asked for.
In one sentence: an API is the counter where two systems ask each other for things, without anyone copying data by hand.
Examples you already use without knowing
You're surrounded by APIs even if you never see them. When you pay with MercadoPago in an online store, the store asks MercadoPago, through its API, whether the payment cleared before shipping. When you sign in "with Google" on a site, that site asks Google to confirm who you are. When you see a map with a store's location, that map comes from an API. When a shipment's tracking updates, the system received the new status from the carrier's API.
The same happens in your business every time two tools pass data to each other. If a person is doing that today, copying from one screen to another, there's an API waiting to replace that manual work.
There's something important here: an API isn't magic, nor open access to everything. It defines what can be asked for and what can't, and with which permissions. It's like the bank window, which handles certain operations and not others, and only for whoever holds the account. That limitation is exactly what makes it secure and orderly.
What it lets you do in your business
With an API integration, two systems that live apart today start sharing information on their own. Some concrete examples:
- Keep inventory in sync between the management system and the online store: a web sale deducts stock in the system, without entering it twice.
- Update prices in one place and have them reflected everywhere.
- Have an order placed on the web land directly in the system, ready to fulfill.
- Issue the electronic invoice from the system itself, without retyping the data.
- Send WhatsApp alerts or automatic notifications from the system.
- Feed a dashboard or report without exporting spreadsheets by hand.
It's always the same idea: data is entered once and travels on its own. That's what removes the copy-and-paste between systems, which is exactly where mistakes show up and time gets lost. This is what I do in integrations and APIs.
What to do if your system has no API
Not every system offers an API. Older ones, desktop programs and many spreadsheets don't, and that's where integration gets harder. Before getting frustrated, there are paths:
- Export and import files. Many systems let you download a CSV or Excel file and upload another. It isn't real time, but it works for daily or weekly processes.
- Ask the vendor. Sometimes the API exists but isn't documented or is only for large customers. It's worth asking before ruling the system out.
- Use a middle tool. Automation platforms (Zapier, n8n) or a small service of your own that translates between the two systems.
- Automate the screen, as a last resort. A robot can use the system the way a person would, but it's fragile: any change to the screen breaks it.
If the system has no API and it's central to your business, sometimes the real decision is another one: evaluating a move to a system that does have one. In CertiCarga, for example, the platform offers an API and webhooks precisely to connect with each transport company's ERP, without forcing them to switch systems.
Webhooks: when the system tells you on its own
There are two ways to find out that something happened. The first is to keep asking: "did the payment arrive? did it arrive? did it arrive?". That's called polling, and it's like calling the bank every five minutes to see if a transfer came in.
The second is for the system to tell you. That's a webhook: instead of you asking, the other system sends you a message at the exact moment something happens, such as a payment clearing, a shipment status changing or an order being created.
The combination of APIs and webhooks is what makes integrations feel instant. It's what CertiCarga uses to notify a company's ERP when there's a new shipment, and what makes tracking update on its own.
The difference: with an API you ask; with a webhook you get told. Good integrations usually use both.
How to keep an integration healthy
An integration isn't something you build once and forget. APIs change, systems get updated and, sooner or later, something stops working. To keep it from breaking silently, it should have three things:
- Visible errors. If a connection fails, someone finds out. No integrations that quietly stop passing data without anyone noticing.
- A log of what happened. What data moved and when, so a problem can be reconstructed.
- Documentation and control. Knowing how it's built and where it lives, so it doesn't depend on a single person.
With that, maintenance is cheaper and the system doesn't fall over by surprise. And when it does need a change, you'll know exactly where to look.
What to ask before buying software
If you're about to buy a system (management, invoicing, a CRM, a store), the API should weigh on the decision. These questions help you sort it out:
- Does it have an API? And if so, is it public and documented?
- What can I do with it? Read data, create records, both? What doesn't it allow?
- Does it have webhooks? Does it notify you when something changes, or can I only poll?
- How does it authenticate? With keys, tokens, per-user permissions.
- Does it have usage limits? How many requests per minute and what happens if I exceed them.
- What does it cost? Some APIs are billed separately or by volume.
- Can I export all my data? Even without an API, keeping your data means not being locked in.
- What happens if I change or close the account? Whether I can take the information with me and what gets lost.
You don't need a technical background to ask these questions; you just need the answers before you sign. A serious vendor has them at hand.
How I approach it
In an integration project I start by mapping what data each system needs and which one is the source of truth for each: for example, inventory lives in the management system and the store reads from it. From that I build the connection with APIs and webhooks, with a log of every movement and alerts when something fails, so it doesn't depend on someone watching. If you want, I'll explain it on a free first call.