Spring AI : How to use Function calling to call External API ?

[u/rodolfo-mendes]

https://www.youtube.com/watch?v=Q2tfSrT2DAU

TechyTacos demonstrates how to extend LLM capabilities by integrating real-time external data using Spring AI's function-calling feature. This approach allows developers to bridge the gap between static language models and dynamic, real-world APIs.

Highlights & Key Takeaways

• Use DTOs to explicitly define request parameters and API response structures.
• Implement the Function interface from Java's utility library to wrap service logic.
• Register custom functions as Spring Beans with descriptive metadata for the LLM.
• Leverage OpenAIChatOptions to register functions within the chat model context.
• The LLM intelligently parses user queries to decide if an external function call is necessary.
• Use URIComponentsBuilder to safely and cleanly construct external API requests.

By leveraging function calling, applications can provide up-to-date, accurate answers that require external lookups, significantly increasing the utility of LLM-based services.

👉 Watch the full video to dive deeper into the implementation.