PydanticAI Instrumentation

Learn how to instrument PydanticAI applications with the LangWatch Python SDK.

LangWatch integrates with PydanticAI through its built-in OpenTelemetry support to capture traces of agent runs and model interactions.

Installation

pip

pip install langwatch pydantic-ai

Usage

The LangWatch API key is configured by default via the LANGWATCH_API_KEY environment variable.

Initialize LangWatch and create your PydanticAI agent. PydanticAI’s built-in OpenTelemetry support will automatically send traces to LangWatch.

from pydantic_ai import Agent
import langwatch

langwatch.setup()

agent = Agent(
    "openai:gpt-5",
    instructions="Be funny, but not too funny.",
)

if __name__ == "__main__":
    result = agent.run_sync("Tell me a joke")
    print(result.output)

LangWatch automatically captures all PydanticAI agent runs and model interactions through PydanticAI’s built-in OpenTelemetry support. Use @langwatch.trace() decorators to add custom traces and metadata as needed.

Related

• Capturing RAG - Learn how to capture RAG data from retrievers and tools
• Capturing Metadata and Attributes - Add custom metadata and attributes to your traces and spans
• Capturing Evaluations & Guardrails - Log evaluations and implement guardrails in your PydanticAI applications