Function Calling (Tool Calling)
The model's ability to trigger external tools: searches, databases, APIs, code execution.
Why it matters
Without tool calling, AI can only generate text. With it, AI takes actions in the real world.
In practice
Claude Code uses tool calling extensively: Read, Write, Bash, Grep, and custom MCP tools — each call logged and approved by the user.
Related terms
Tool Use
An agent's ability to call external tools: searches, databases, APIs, code execution.
MCP (Model Context Protocol)
An open standard for connecting AI tools to external services. "USB-C for AI."
Agent (AI Agent)
An AI system that plans, decides, and acts autonomously toward goals, rather than simply responding to prompts.
Dynamic Tool Selection
An agent's ability to choose which tools to use based on the task at hand.