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Understand how models call external functions and tools to take action.
6 conceptsFunction Calling
Function calling lets a model request that a specific function be executed with structured arguments it generates.
Intermediate · 4 minTool Calling
Tool calling is the general pattern of a model invoking external tools to take actions or fetch information it can't produce on its own.
Intermediate · 4 minTool Schema
A tool schema describes a tool's name, purpose, and expected input format so a model knows how to call it correctly.
Intermediate · 3 minTool Input
Tool input is the structured data a model generates to call a tool according to its schema.
Intermediate · 3 minTool Result
A tool result is the output returned from a tool call, which the model uses to continue its response.
Intermediate · 3 minAPI Tools
API tools wrap external APIs so a model can call real services, such as search, weather, or internal systems, as tools.
Intermediate · 4 min