Pydantic AI Cheat Sheet — Agents & Tools Reference

from pydantic_ai import Agent
from pydantic_ai.tools import Tool
import os

agent = Agent(
    model='openai:gpt-4o',
    api_key=os.environ['OPENAI_API_KEY']
)

@agent.tool
def get_weather(location: str) -> str:
    return f'Sunny in {location}'

result = agent.run_sync('What is the weather in NYC?')
print(result.data)

from pydantic import BaseModel
from pydantic_ai import Agent
import os

class UserProfile(BaseModel):
    name: str
    age: int
    interests: list[str]

agent = Agent(
    model='openai:gpt-4o',
    result_type=UserProfile,
    api_key=os.environ['OPENAI_API_KEY']
)

result = agent.run_sync('Create a profile for Alice, 28, likes Python')
print(result.data.name)  # Alice
print(result.data.age)   # 28

from pydantic_ai import Agent, RunContext
from pydantic import BaseModel
import os

class DependencyState(BaseModel):
    user_id: str
    api_token: str

agent = Agent(
    model='openai:gpt-4o',
    deps_type=DependencyState,
    api_key=os.environ['OPENAI_API_KEY']
)

@agent.tool
def get_user_data(ctx: RunContext[DependencyState], key: str) -> str:
    # ctx.deps has user_id and api_token
    return f'User {ctx.deps.user_id}: {key}'

deps = DependencyState(
    user_id='user123',
    api_token=os.environ['API_TOKEN']
)
result = agent.run_sync('Get my name', deps=deps)
print(result.data)

from pydantic_ai import Agent, ModelMessage
import os

agent = Agent(
    model='openai:gpt-4o',
    api_key=os.environ['OPENAI_API_KEY']
)

messages: list[ModelMessage] = []

# Turn 1
result1 = agent.run_sync('My name is Alice', messages=messages)
messages.extend(result1.messages())

# Turn 2
result2 = agent.run_sync('What did I say my name was?', messages=messages)
messages.extend(result2.messages())
print(result2.data)  # Will reference Alice from turn 1

from pydantic_ai import Agent
import os

agent = Agent(
    model='openai:gpt-4o',
    system_prompt='You are a sarcastic Python expert. Always suggest dataclasses over dicts.',
    api_key=os.environ['OPENAI_API_KEY']
)

@agent.tool
def explain_code(snippet: str) -> str:
    return f'Explaining: {snippet}'

result = agent.run_sync('How do I store user data?')
print(result.data)

from pydantic_ai import Agent
import asyncio
import os

agent = Agent(model='openai:gpt-4o', api_key=os.environ['OPENAI_API_KEY'])

@agent.tool
async def fetch_api(url: str) -> str:
    # Simulate async I/O
    await asyncio.sleep(0.1)
    return f'Data from {url}'

async def main():
    result = await agent.run('Fetch data from API')
    print(result.data)

asyncio.run(main())