Building Your First Agent

Step-by-step guide to creating a functional agent.

Manual ReAct Agent

Building the ReAct pattern by hand with StateGraph gives you full control over every node, edge, and routing decision in the agent loop.

Prebuilt ReAct Agent

create_react_agent from langgraph.prebuilt is the highest-level abstraction for building a fully functional tool-calling agent in under 10 lines of code.

Structured Output

model.with_structured_output(Schema) forces LLM responses into typed Pydantic models, turning free-form text into reliable, parseable data structures.

Tool-Calling Loop

The tool-calling loop is the fundamental cycle where an LLM reasons about a task, invokes tools, observes results, and repeats until it can answer without further tool use.