What Is Tool Use / Function Calling?
Tool use (also called function calling) is an AI capability that allows language models to invoke external tools, APIs, and functions by generating structured requests, enabling them to take real-world actions, access current data, and perform computations beyond their native text generation abilities.
How Tool Use / Function Calling Works
Language models are powerful at understanding and generating text, but they have inherent limitations: they cannot browse the web, run code, query databases, or take actions in the real world on their own. Tool use bridges this gap by training models to recognize when a tool would help and to generate properly formatted function calls. The model outputs a structured JSON request specifying which tool to call and with what parameters, the system executes the tool, and the result is fed back to the model for incorporation into its response. OpenAI, Anthropic, and Google all support tool use in their APIs. This capability is the foundation of agentic AI, enabling models to become active participants in workflows rather than passive text generators.
Real-World Examples
ChatGPT calling a weather API function to get current conditions when a user asks 'What's the weather in Tokyo?'
Claude generating a structured function call to a calculator tool when asked to compute compound interest precisely
An AI assistant using function calling to create a calendar event, send an email, and update a CRM record in a single interaction
Tool Use / Function Calling on Vincony
Vincony enables tool use across its platform, letting AI models access external data and services to provide more accurate, action-oriented responses.
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