Recently, the demand for remote counseling has been on the rise using conversational agents with Large Language Models (LLM) in many areas. This LLM trend is expanding beyond generating simple words to constructing complex sentences, showing progress in various fields. The significant development of LLM is attributed to the progress in Natural Language Processing (NLP) technology, built upon extensive language data. This study introduces a client technology of Open API System based conversational agent using LLM. The target agent is a Chatbot which can generate health counseling messages including empathetic conversations for users with caring his chronic conditions requiring ongoing health management. The overall system can be linked with the community care system through user APPs and APIs for digital healthcare context management. The advantage with the client with REST API is that APIs make it easy to integrate new applications with existing software systems, allowing target systems to meet requirements across a variety of platforms.