LangSmith API

langchain.com

Provides tracing, evaluation, observability, and deployment infrastructure for LLM and agent applications via SDKs and API endpoints.

The LangSmith API API has freemium pricing; offers a free tier (Developer plan $0/seat: up to 5k base traces/mo, then pay-as-you-go, 1 seat). Verified 2026-07-13 with per-field source links.

Developer Tools Verified 2026-07-13 medium confidence

Base URL

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Auth

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Free tier

Developer plan $0/seat: up to 5k base traces/mo, then pay-as-you-go, 1 seat

langchain.com ↗

Pricing model

freemium

langchain.com ↗

Pricing

Developer $0/seat (5k base traces/mo); Plus $39/seat/mo (10k base traces/mo); Enterprise custom. Base traces $2.50/1k, extended traces $5.00/1k; deployment runs $0.005 each; Engine $1.50/LCU

langchain.com ↗

Rate limits

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OpenAPI spec

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MCP server

Deployment can expose agent as MCP server; native protocol support for A2A & MCP

langchain.com ↗