An application programming interface (API) is a defined set of rules that lets software applications communicate. One application sends a request to an exposed endpoint, often a URL, with parameters describing the needed data or action; the API then returns data or performs the action. section 2.2
A typical API interaction moves through these stages:
- Choose the endpoint representing the available operation. section 2.2
- Send a request with parameters that specify the required data or action. section 2.2
- Authenticate the request, typically with an API key. section 2.2
- Receive returned data or the result of the requested action. section 2.2
APIs turn GenAI applications from conversational systems into participants in a broader software ecosystem. They can retrieve data, update records, send messages, book meetings, or control connected devices. LLMs may decide what should happen, but APIs and other tools perform the external action. section 5.1 section 8.6
Expose a GenAI flow as an HTTP API
A Langflow email-generation flow can become a FastAPI service. A POST /generate-email endpoint accepts a customer profile as JSON and returns a structured response containing the email subject and body. External systems can call the service without using a chat interface. section 7.3
Figure 2.4 An API key is typically required to authenticate the request.
Use the figure to visualize how an API key authenticates a request. section 2.2
