What is Function Calling?
An AI model's ability to output structured requests to invoke external functions, APIs, or tools during a conversation.
Definition
Function calling is a capability where language models generate structured output (typically JSON) that specifies which external function to call and with what arguments, rather than generating a text response. The application then executes the function and returns the result to the model, which incorporates it into its response. This enables AI to interact with databases, APIs, calculators, and any programmatic tool. OpenAI, Anthropic, and Google all support function calling in their APIs. Functions are defined with name, description, and parameter schemas. The model decides when and which functions to call based on the user's request and function descriptions.
Examples
Why It Matters
Function calling transforms AI from a text generator into an action-taker. It is the foundation for AI assistants that can search the web, run code, manage calendars, and interact with any software system.
Related Terms
Tool Use
An AI model's ability to select and invoke external tools like search engines, calculators, or code interpreters.
Prompt Chaining
Breaking complex AI tasks into sequential prompts where each step's output feeds into the next step's input.
Multi-Agent Systems
Architectures where multiple specialized AI agents collaborate, debate, or coordinate to solve complex tasks.
AI Orchestration
Managing and coordinating multiple AI models, tools, and workflows to complete complex end-to-end tasks.
Common Questions
What does Function Calling mean in simple terms?
An AI model's ability to output structured requests to invoke external functions, APIs, or tools during a conversation.
Why is Function Calling important for AI users?
Function calling transforms AI from a text generator into an action-taker. It is the foundation for AI assistants that can search the web, run code, manage calendars, and interact with any software system.
How does Function Calling relate to AI chatbots like ChatGPT?
Function Calling is a fundamental concept in how AI assistants like ChatGPT, Claude, and Gemini work. For example: Model calling get_weather(city="London") to provide current weather in a response Understanding this helps you use AI tools more effectively.
Related Use Cases
AI Models Using This Concept
See Function Calling in Action
Council lets you compare responses from multiple AI models side-by-side. Experience different approaches to the same prompt instantly.