How To Build A Multi Agent System With Crewai

When to reach for CrewAI

This guide builds a working three-agent crew in Python, explains the four primitives (Agent, Task, Crew, Tool), and flags the failure modes you’ll hit once you put one on a schedule. Written April 2026.

Step 1 — Install

CrewAI’s biggest trap is verbose backstories. Keep them to one or two sentences. A long backstory eats context and distracts the model. If your “Writer” agent is drifting, cut the backstory, not the goal.

Step 2 — The four primitives

Every agent is a separate model call. A 3-agent sequential crew with retries can easily hit 15–20 turns. Before you put one on a schedule:

Step 3 — A three-agent crew

Step 4 — Run it

Step 5 — Tighten the prompts

Step 6 — Sequential vs. hierarchical

Step 7 — Cost control

Step 8 — Schedule it

Common mistakes