Skip to main content

Documentation Index

Fetch the complete documentation index at: https://docs.langchain.com/llms.txt

Use this file to discover all available pages before exploring further.

LangSmith can capture traces generated by PydanticAI using its built-in OpenTelemetry instrumentation. This guide shows you how to automatically capture traces from your PydanticAI agents and send them to LangSmith for monitoring and analysis.

​
Installation

Install the required packages: 
pip install langsmith pydantic-ai opentelemetry-exporter-otlp
Requires LangSmith Python SDK version langsmith>=0.4.26 for optimal OpenTelemetry support.

​
Setup

​
1. Configure environment variables

Set your API keys and project name: 
export LANGSMITH_API_KEY=<your_langsmith_api_key>
export LANGSMITH_PROJECT=<your_project_name>
export OPENAI_API_KEY=<your_openai_api_key>

​
2. Configure OpenTelemetry integration

In your PydanticAI application, configure the LangSmith OpenTelemetry integration: 
from langsmith.integrations.otel import configure
from pydantic_ai import Agent

# Configure LangSmith tracing
configure(project_name="pydantic-ai-demo")

# Instrument all PydanticAI agents
Agent.instrument_all()
You do not need to set any OpenTelemetry environment variables or configure exporters manually—configure() handles everything automatically.

​
3. Create and run your PydanticAI agent

Once configured, your PydanticAI agents will automatically send traces to LangSmith: 
from langsmith.integrations.otel import configure
from pydantic_ai import Agent

# Configure LangSmith tracing
configure(project_name="pydantic-ai-demo")

# Instrument all PydanticAI agents
Agent.instrument_all()

# Create and run an agent
agent = Agent('openai:gpt-5.4')
result = agent.run_sync('What is the capital of France?')
print(result.output)
#> Paris

​
Advanced usage

​
Custom metadata and tags

You can add custom metadata to your traces using OpenTelemetry span attributes: 
from opentelemetry import trace
from pydantic_ai import Agent
from langsmith.integrations.otel import configure

configure(project_name="pydantic-ai-metadata")
Agent.instrument_all()

tracer = trace.get_tracer(__name__)

agent = Agent('openai:gpt-5.4')

with tracer.start_as_current_span("pydantic_ai_workflow") as span:
    span.set_attribute("langsmith.metadata.user_id", "user_123")
    span.set_attribute("langsmith.metadata.workflow_type", "question_answering")
    span.set_attribute("langsmith.span.tags", "pydantic-ai,production")

    result = agent.run_sync('Explain quantum computing in simple terms')
    print(result.output)
Connect these docs to Claude, VSCode, and more via MCP for real-time answers.
Edit this page on GitHub or file an issue.