LangSmith by LangChain
Tracing, evaluation and monitoring of LLM apps and agents, including prompt and dataset management.
LLM observability and evals Official MCP server
＋ Build a stack with LangSmith Website Official pricing GitHub
Price
Free plan
then from $39/mo
Free tier
Yes
Developer plan: 1 seat, up to 5k base traces / mo, then...
SDK downloads
—
npm langsmith · PyPI langsmith
Pricing
| Free tier | Developer plan: 1 seat, up to 5k base traces / mo, then pay-as-you-go |
|---|---|
| Cheapest paid plan | $39 a month |
| Usage price | Plus: $39 / seat per month incl. up to 10k base traces / mo; trace overage is pay-as-you-go (rate not listed on pricing page); 1 LSU = $1 (Deployment/Fleet/Sandbox usage) |
| Good to know | Base traces have 14-day retention, extended traces 180-day retention at an extra fee. Enterprise is custom pricing. |
From the official pricing page, checked Oct 10, 2026. Prices change: confirm before you buy.
Use it from an agent
| MCP server | Official: https://docs.langchain.com/langsmith/langsmith-mcp-server |
|---|---|
| npm | npm install langsmith |
| PyPI | pip install langsmith |
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