Concept beginner · 3 min read

What is LangSmith

Quick answer
LangSmith is an AI observability platform that automatically traces and monitors large language model (LLM) calls to help developers debug, analyze, and optimize AI applications. It integrates with popular AI SDKs and frameworks to provide detailed insights into model usage and performance.
LangSmith is an AI observability platform that tracks and analyzes LLM calls to improve AI application reliability and debugging.

How it works

LangSmith works by automatically tracing all interactions between your application and large language models (LLMs). It collects metadata, inputs, outputs, and performance metrics for each API call. This data is then visualized in a dashboard, enabling developers to monitor usage patterns, detect anomalies, and debug issues efficiently. Think of it as an application performance monitoring tool but specialized for AI model calls.

Concrete example

To enable tracing with LangSmith, set environment variables and import the langsmith Python SDK. Here is a minimal example that wraps an OpenAI client to trace calls automatically:

python
import os
from openai import OpenAI
from langsmith import Client, traceable

os.environ["LANGCHAIN_TRACING_V2"] = "true"
os.environ["LANGCHAIN_API_KEY"] = os.environ["LANGSMITH_API_KEY"]
os.environ["LANGCHAIN_PROJECT"] = "my-ai-project"

langsmith_client = Client(api_key=os.environ["LANGSMITH_API_KEY"])

@traceable()
def generate_text(prompt: str) -> str:
    client = OpenAI(api_key=os.environ["OPENAI_API_KEY"])
    response = client.chat.completions.create(
        model="gpt-4o-mini",
        messages=[{"role": "user", "content": prompt}]
    )
    return response.choices[0].message.content

result = generate_text("Explain retrieval-augmented generation.")
print(result)
output
Retrieval-augmented generation (RAG) is an AI technique that combines a retrieval system with a language model to generate answers grounded in specific knowledge bases.

When to use it

Use LangSmith when building AI applications that require robust monitoring, debugging, and performance analysis of LLM calls. It is ideal for production environments where understanding model behavior, latency, and error rates is critical. Avoid using it for simple prototypes or experiments where observability overhead is unnecessary.

Key terms

TermDefinition
LLMLarge Language Model used for generating or understanding text.
TracingAutomatic recording of API calls and metadata for observability.
ObservabilityAbility to monitor and analyze system behavior and performance.
LangChainA popular framework for building AI applications, integrated with LangSmith.
API KeyAuthentication token used to access LangSmith and AI services.

Key Takeaways

  • LangSmith automatically traces LLM calls to improve AI application observability.
  • It integrates seamlessly with popular AI SDKs like OpenAI and LangChain.
  • Use LangSmith to debug, monitor, and optimize production AI workloads effectively.
Verified 2026-04 · gpt-4o-mini
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