Glossary

Tool Use (Function Calling)

Tool use — also called function calling — is the capability of a language model to emit structured calls to external tools, enabling an agent to take real actions in connected systems.

When a user asks an AI agent to do something that requires action — looking up an order, creating a ticket, scheduling a meeting — the model decides to call a tool. It emits a structured request (tool name, arguments), the agent runtime executes that request against the appropriate system, and the result is passed back to the model to continue reasoning.

Tool use is what separates an AI agent from a conversational text generator. Without it, the model can only talk about actions; with it, the model can actually take them. The quality of the tool surface — which tools exist, how they're described, how their outputs are shaped — heavily influences how well the agent performs.

In enterprise deployments, tool surfaces are typically exposed via an MCP server so the same tools can be consumed by multiple agents and model versions, and so governance controls can be applied consistently.

See also
  • AI Agent— An AI agent is a software system that uses a large language model to perceive its environment, reason about tasks, and take actions in external systems on behalf of a user.
  • Model Context Protocol (MCP)— Model Context Protocol (MCP) is an open standard for connecting AI agents to the tools, data sources, and prompts they need, through a consistent client-server protocol.
  • Retrieval-Augmented Generation (RAG)— Retrieval-augmented generation (RAG) is an architecture that grounds a language model's responses in a specific knowledge base by retrieving relevant passages at inference time and conditioning the response on them.
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More terms in the glossary

AI Agent

An AI agent is a software system that uses a large language model to perceive its environment, reason about tasks, and take actions in external systems on behalf of a user.

AI Voice Agent

An AI voice agent is an AI agent that interacts with users through voice — answering inbound calls, placing outbound calls, and conversing in real time.

AI Chatbot (AI Chat Agent)

An AI chatbot — more accurately, an AI chat agent — is an AI agent that interacts with users through text: web chat, WhatsApp, SMS, Slack, Teams, or social messaging.

Retrieval-Augmented Generation (RAG)

Retrieval-augmented generation (RAG) is an architecture that grounds a language model's responses in a specific knowledge base by retrieving relevant passages at inference time and conditioning the response on them.

Multi-Agent Orchestration

Multi-agent orchestration is the practice of coordinating multiple specialized AI agents to accomplish a task that is too complex or too broad for a single agent.

Constitutional AI

Constitutional AI is an approach to training and deploying AI systems in which model behavior is guided by an explicit written set of principles — a "constitution" — rather than only by reinforcement from human feedback.

See the full glossary

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