🔍 What is LangSmith?
LangSmith is a developer platform that helps you observe, debug, monitor, and evaluate your AI agents and LLM-powered applications.
If you’ve built something with LangChain or LangGraph, LangSmith shows you exactly what’s happening under the hood.
🚗 Why Do You Need LangSmith?
Imagine building a self-driving car without a dashboard you wouldn’t know what’s going wrong or right. LangSmith is that dashboard for your AI agents.
🧩 Use LangSmith when:
- Your AI output feels inconsistent or unpredictable.
- You want to understand which part of the prompt/tool/chain is failing.
- You want to track token usage and optimize costs.
- You need to evaluate, test, and improve AI workflows before deploying them.
🛠️ What LangSmith Helps You Do
1. Observability
Track every step your agent takes: prompts, responses, tools used, and final output.
2. Tracing Projects
View the call stack of your agent’s logic similar to debugging in code so you can catch and fix errors.
3. Monitoring
See trends across your app usage, latency, success/failure rates, and more.
4. Evaluation
Compare different prompts or workflows side by side and choose the best-performing one.
5. Datasets & Experiments
Test how your app performs with various inputs. Great for structured testing or user feedback loops.
6. Prompt Engineering
Write, test, and refine prompts in an organized and measurable way.
7. Playground
Try out prompts or chains on the fly experiment before pushing to production.
🧠 LangSmith + LangChain + LangGraph = Production-Ready AI
Think of it like this: Tool Purpose
LangChain The brain — logic and memory
LangGraph The nervous system — workflow control
LangSmith The health monitor — what’s happening, where, and how well
🚦 Roadmap & Setup
🧱 Step-by-Step LangSmith Setup
Install LangChain (includes LangSmith features)
pip install langchain
Set up LangSmith environment:
import os
import langchain
langchain.debug = True
os.environ["LANGCHAIN_API_KEY"] = "your-api-key"
os.environ["LANGCHAIN_ENDPOINT"] = "https://api.smith.langchain.com"
os.environ["LANGCHAIN_TRACING_V2"] = "true"
os.environ["LANGCHAIN_PROJECT"] = "AI-Workflow-Demo"
Run your agent/chain as usual. All executions are now visible in your LangSmith dashboard under Projects → Traces.
💰 How to Calculate Token Usage (Python Example)
Want to know how much your usage will cost? Here’s a simple calculator:
For GPT-3.5 Turbo (1M tokens)
def calculate_cost(model, tokens):
prices = {
"gpt-3.5-turbo": 0.0005, # per 1K tokens
"gpt-4.0-nano": 0.003, # hypothetical example
}
return tokens / 1000 * prices.get(model, 0)
model = "gpt-3.5-turbo"
tokens = 1_000_000
print(f"Cost for {tokens} tokens using {model}: ${calculate_cost(model, tokens):.2f}")
Use this to keep track of expenses before scaling your app.
📈 Where to Find What in LangSmith
- Projects: Organize work by use case or client.
- Traces: See individual agent runs, logic steps, tools, memory.
- Observability: Performance metrics and token usage.
- Evaluation: Compare prompt effectiveness.
- Playground: Test ideas in real time.
- Deployments: Launch APIs from workflows.
- LangGraph Platform: View visual workflows and state graphs.
🔥 Example to Tie It All Together
Problem:
You’re building a content marketing AI agent that:
- Researches trends
- Writes blog outlines
- Generates content
- Suggests headlines
- Emails it to your team
Agentic Workflow:
- LangChain: Defines the logic (tools like search, writer, emailer)
- LangGraph: Structures the steps: Search → Outline → Write → Review → Send
LangSmith:
- Lets you observe when the “Write” step takes too long
- Shows that 70% of failures happen during “Review”
- Helps you optimize prompts and evaluate versions
- Lets you compare costs and reduce token usage by tweaking memory
Now you have:
- A smart content AI agent
- Observability to debug it
- Cost tracking
- Evaluation data to improve it
All without writing complex code.
My DashBoard
🤖 Common Questions Answered
Question Can I use LangSmith without LangGraph? Yes works with any LangChain app.
Does it store sensitive data? You can choose to redact or anonymize inputs.
Is it for devs only? No. The UI is beginner-friendly and helps prompt engineers too.
Can I export reports? Yes. Use datasets and evaluations.
🌟 Final Thoughts
LangSmith is what turns an LLM demo into a production-grade AI agent. It’s your debugger, tester, optimizer, and token tracker all in one dashboard.
If you’re building agents that need to be smart, scalable, and reliable, LangSmith is not optional it’s essential.