What is an API? Why your business software should talk to each other

An API (application programming interface) is a set of agreed rules that lets one piece of software ask another for information or tell it to do something, without a person in between. When your website, payment provider, courier, accounts and team chat can talk through APIs, an order typed once flows everywhere it needs to go. When they cannot, someone on your team becomes the connection, copying and pasting all day.

An everyday way to picture it

Think of a courier office counter. You do not walk into the warehouse and load your parcel onto a truck yourself. You go to the counter, fill in a standard form (sender, receiver, address, weight), and the counter staff take it from there. Later you can ask at the same counter, "Where is parcel number such-and-such?" and get a standard answer.

An API is that counter for software. It sets out:

• What you can ask for: an order's status, a list of today's payments, a customer's details.
• What you can tell it to do: create a delivery, send an SMS, add an invoice.
• What form the request must take: which fields, in which format.
• Who is allowed to ask: usually checked with a secret key or a login token.

The other software's inner workings stay private. You only use the counter.

Examples you already rely on

You probably use APIs every day without seeing them:

• When a website shows a map of your shop, it is asking a map service through its API.
• When an online payment succeeds and the website instantly marks the order as paid, the payment gateway has told the website through an API.
• When a courier's tracking status appears inside an online shop, the shop has asked the courier's system.
• When you sign in to a site "with Google", the two systems are talking through APIs.

Why your software should talk to each other

Most small and medium businesses in Bangladesh run on a mix of tools: a Facebook page, WhatsApp, a spreadsheet, an accounting program, perhaps a website and a courier account. Each holds part of the picture. When they are not connected, three things happen.

1. Double entry. The same order is typed into the sheet, the courier portal and the accounts. Every retyping takes time and invites mistakes in phone numbers, amounts and addresses.
2. Delays. The owner only sees today's sales once someone compiles them, often late in the evening or the next day.
3. Disagreement. The sheet says one thing, the accounts say another, and nobody is sure which is right.

When the systems are connected, information is entered once, at the source, and copied automatically. Staff time moves from typing to checking and serving customers.

What "integration" involves

Connecting two systems is not always a single switch. A typical integration needs:

• Documentation. The provider publishes how its API works. Clear documentation is a good sign of a serious provider.
• Access keys. Secret credentials that prove your system is allowed to connect. They must be stored safely, never pasted into a public page or a shared chat.
• A way to hear about events. Either your system checks regularly ("Any new payments?"), or the other system sends a notice the moment something happens, often called a webhook.
• Mapping. Deciding which field in one system matches which field in the other, for example "district" in your order form and "area" in the courier's system.
• Error handling. What happens if the other system is down, the internet drops during a power cut, or a request is rejected. A solid integration retries, logs the failure and alerts a person.

Questions to ask before you buy any software

Whether it is accounts software, a point-of-sale system or a booking tool, ask the vendor:

• Does it have an API, and is the documentation public?
• Can it send notices (webhooks) when something changes?
• Can I export all my data in a standard format if I leave?
• Are there limits on how often the API can be used?
• Does it already connect to the tools I use, or will custom work be needed?

A product with no API is an island. It may look cheap today and turn out costly later, when someone has to retype its data for as long as you use it.

Where to go from here

List the tools your business uses and draw a line between each pair where someone copies information by hand. Those lines are your integration opportunities. Common first candidates are matching bKash, Nagad and bank payments with sales and taking online payments on your website through a licensed gateway. Some links can be made with no-code tools; others need custom work, which I handle as part of my AI and workflow automation service.