Definition
An API (Application Programming Interface) is a bridge that allows two software programs to "talk" to each other. It defines the correct way for a developer to request services from an operating system, library, or another application.
APIs in the AI Era
In the context of modern AI, APIs have two primary roles:
1. Consuming AI (Model-as-a-Service)
Most developers don't train their own Large Language Models. Instead, they use APIs provided by companies like OpenAI, Anthropic, or Google. By sending a request to their API, a developer can add "intelligence" to their own app without needing massive hardware.
2. Empowering AI Agents (Tool Calling)
AI Agents use APIs to perform actions. When you ask an agent to "book a flight," it doesn't physically type on a keyboard; it sends a structured request to a travel site's API. This process is often called "Tool Calling" or "Function Calling."
Key Concepts
- REST (Representational State Transfer): The most common architectural style for web APIs.
- JSON (JavaScript Object Notation): The standard format for data exchange between APIs and AI models.
- Authentication (API Keys): A security measure to ensure only authorized users can access the API.
- Rate Limiting: Restrictions on how many requests can be made in a certain timeframe.
Standardizing AI APIs
The industry is moving toward standardizing how AI interacts with tools. One major effort is the Model Context Protocol (MCP), which provides a universal way for agents to connect to any data source or tool through a standardized API.