APIAPI
A standardised way for software to talk to other software.
An API (Application Programming Interface) is a contract that defines how two pieces of software communicate. It specifies the available endpoints, what inputs to send, and what outputs to expect — without exposing any internal code.
When you use a weather app, it calls a weather service API. When you query an AI, your code sends an HTTP request to the model's API with your prompt, and receives a JSON response.
For AI products, key APIs are the model inference APIs (Anthropic, OpenAI, Google) and tool APIs that agents can call — search, databases, CRMs. Every connector, skill, and MCP server ultimately communicates through APIs.
In plain terms
An API is a restaurant menu. You choose items (endpoints), provide your order (request), and receive your meal (response) — without entering the kitchen (source code).