Pydantic AI

Tools & Dependency Injection Example

Here is a concise example using Pydantic AI to build a support agent for a bank:

(Better documented example in the docs)

```python from dataclasses import dataclass

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

from bank_database import DatabaseConn

SupportDependencies is used to pass data, connections, and logic into the model that will be needed when running

instructions and tool functions. Dependency injection provides a type-safe way to customise the behavior of your agents.

@dataclass class SupportDependencies: customer_id: int db: DatabaseConn

Agents are generic in the type of dependencies they accept and the type of output they return.

In this case, the support agent has type `Agent[SupportDependencies, SupportOutput]`.

support_agent = Agent( 'openai:gpt-5.2', deps_type=SupportDependencies, # The response from the agent will be guaranteed to be a SupportOutput, # if validation fails the agent is prompted to try again. output_type=SupportOutput, instructions=( 'You are a support agent in our bank, give the ' 'customer support and judge the risk level of their query.' ), )

Dynamic instructions can make use of dependency injection.

Dependencies are carried via the `RunContext` argument, which is parameterized with the `deps_type` from above.

Again, dependencies are carried via `RunContext`, any other arguments become the tool schema passed to the LLM.

<em>Pydantic AI is a Python agent framework designed to help you quickly, confidently, and painlessly build production grade applications and workflows with Generative AI.</em>

FastAPI revolutionized web development by offering an innovative and ergonomic design, built on the foundation of Pydantic Validation and modern Python features like type hints.

Yet despite virtually every Python agent framework and LLM library using Pydantic Validation, when we began to use LLMs in Pydantic Logfire, we couldn't find anything that gave us the same feeling.

We built Pydantic AI with one simple aim: to bring that FastAPI feeling to GenAI app and agent development.

Hello World Example

Here's a minimal example of Pydantic AI:

```python from pydantic_ai import Agent