What is Tool Use (Function Calling)? - Definition & Meaning
Learn what Tool Use and Function Calling are, how LLMs invoke external tools and APIs, and why it is essential for practical AI applications.
Definition
Tool Use (Function Calling) is the ability of LLMs to invoke external functions, APIs, or tools during a conversation. The model decides when a tool is needed and which parameters to pass; the tool is executed and the result is returned.
Technical explanation
The developer defines tools as JSON schemas (name, description, parameters). The LLM receives a user message, chooses a tool or generates a response, and returns a tool call. The application executes the function (database query, API call, calculation) and sends the result back. The LLM incorporates it into its answer. OpenAI, Anthropic, and Google support native function calling. LangChain and LlamaIndex abstract this with tool wrappers. Multi-tool chains are possible: search → retrieve → summarize.
How AVARC Solutions applies this
AVARC Solutions implements function calling in virtually every LLM project: from chatbots querying business data to agentic workflows integrating CRM and email. We define strict tool schemas and validate parameters for safety.
Practical examples
- A customer service chatbot using function calling to look up orders, check inventory, and create tickets.
- A booking assistant checking availability, fetching prices, and making reservations via tools.
- A data analyst agent generating SQL queries, executing them via a tool, and interpreting results.
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Frequently asked questions
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