API and low-code development is the way most new apps are built today: from ready-made parts joined together, instead of writing every piece from scratch. The parts are joined through APIs. An API, or application programming interface, is a fixed set of requests that one program accepts from other programs. For example, a payment company's API accepts the request "collect ₹499 from this customer" and replies with the result. Low-code is the other half: platforms on which apps are built by dragging screens and forms together, with little hand-written code.
Imagine a team of four developers at a logistics start-up in Ahmedabad. They are building an app that lets shop owners book a parcel pickup and track the parcel.
They do not write everything themselves. Payments come from a payment company's API. Maps come from a map provider's API. Messages to the customer, such as "your parcel is out for delivery", go through a notification service. The app makes one API call, and the service sends an SMS, an email or a WhatsApp message.
The team's own code is split into APIs too. One service handles bookings, another tracks parcels, and a third works out prices. The developers design and try out each API in an API development platform. There, they write down what each request looks like and what it returns. The standard file format for this description is the OpenAPI specification.
All requests from the app to these services pass through an API gateway. The gateway sends each request to the right service, checks that the caller is allowed in, and counts every call.
For the app's screens, the developers use UI component libraries. These are ready-made screen parts, such as tables, charts, date pickers and forms. A table that sorts and filters 10,000 parcels takes a few lines of code instead of weeks of work.
The operations team needs internal tools as well: a screen to reassign pickups when a rider is ill, and a form to record damaged parcels. Nobody has time to code them. So one developer builds them on a low-code platform in two days. She drags a table, a form and a button onto a page, and connects them to the booking API.
A new kind of caller is now arriving. AI agents, software that uses a language model to take actions on its own, call APIs too. So APIs are now described in a way that an agent can read and use correctly. The page on AI agent guardrails explains why an agent must be given only the access it needs.
Many of these building blocks are free open-source software, which companies make into a business by selling support and extra features. And a founder with no developers at all can now ask an AI app builder to produce a whole app from a plain-language description.