CrewAI vs Pydantic AI: Which Agent Framework to Use?

CrewAI models work as a team metaphor: Agent(role, goal, backstory) plus Task plus Crew(process=sequential|hierarchical). Pydantic AI models work as a typed function call: Agent with a result_type Pydantic model, @agent.tool decorators with typed parameters, and RunContext[DepsType] for dependency injection.

One treats agents as personas you orchestrate; the other treats them as schemas you validate. CrewAI optimizes for prompt-level role separation, Pydantic AI for compile-time type checks on tool args and outputs.

CrewAI is the bigger community by raw numbers — ~48k GitHub stars vs ~16k — and ships memory primitives (ShortTermMemory, LongTermMemory, EntityMemory) plus first-class MCP support. Pydantic AI is younger (June 2024) but inherits the Pydantic user base and pairs natively with Logfire for tracing.

Both are MIT, both are Python-only. CrewAI leans toward plug-and-play multi-agent demos; Pydantic AI leans toward integration into existing typed Python codebases (FastAPI, SQLModel, Pydantic-heavy stacks).

Use CrewAI when you actually have multiple specialists collaborating — researcher → writer → editor — and the orchestration between roles is the hard part. The process=hierarchical flag and built-in delegation guardrails matter when one agent needs to route work to another.

Use Pydantic AI when a single agent's outputs feed into typed downstream systems and a malformed tool_call is a production bug. Its 25+ provider abstraction (model='openai:gpt-4o' → model='anthropic:claude-sonnet') also matters more than CrewAI's role vocabulary if you swap models often.

Pick crewai if your project lives or dies on coordinating multiple agents with distinct roles and handoffs.

• Role-driven prompt design: You want role, goal, and backstory as first-class fields so prompt engineering for a "Senior Researcher" vs a "Copy Editor" stays organized as the crew grows.
• Hierarchical or sequential orchestration: Crew(process=hierarchical) with manager-driven delegation is closer to your workflow than a hand-rolled task queue, and you want delegation guardrails out of the box.
• Built-in memory tiers: You need ShortTermMemory, LongTermMemory, and EntityMemory distinctions without designing your own retrieval layer.

Pick pydantic-ai if your project lives or dies on typed contracts between the agent and the rest of your code.

• Structured outputs into typed systems: result_type=CustomerRecord enforces a Pydantic model on the final response, so downstream code never sees a malformed dict from the LLM.
• Existing Pydantic / FastAPI stack: Your team already writes Pydantic models everywhere; @agent.tool with typed params and RunContext[DepsType] slots into that style without a new mental model.
• Frequent model switching: You toggle between openai:gpt-4o, anthropic:claude-sonnet, and others often enough that the unified provider interface plus Logfire tracing pays for itself.

Both frameworks add a class hierarchy you have to learn before you can ship: Agent / Task / Crew / process in CrewAI, Agent / result_type / @agent.tool / RunContext in Pydantic AI. That ramp-up is real, and so is the lock-in — once tools are decorated and crews are wired, ripping the abstraction out is non-trivial.

Both also hide the loop. The actual mechanics — call LLM, dispatch tool, validate, repeat — happen inside agent.run() or Crew.kickoff(), which makes debugging tool-call failures or token budgets harder than reading a 30-line while loop.