LangSmith: Agent Traces, Evaluation and Platform Pricing
What does LangSmith do?
LangSmith provides observability for LLM applications, with traces, performance views and feedback workflows. Its documentation connects production traces to datasets used for evaluation and lists integrations across multiple frameworks. Teams should choose the services they need rather than treating the broader platform as one undifferentiated product.
Who is it for?
Developers operating agent applications may need to follow a conversation across model and tool calls. The first useful question is usually which step caused an incorrect outcome. If you only need occasional offline prompt comparisons, a smaller evaluation setup may be easier to maintain.
What does pricing include?
Developer is listed at $0 per seat per month for one seat, with 5,000 base traces per month before pay-as-you-go usage. Plus is $39 per seat per month and lists 10,000 base traces. Deployment, model gateway and other services have their own metering. Compare the current billing units and retention terms before estimating a complete agent workload.
How can you evaluate the workflow?
Create a synthetic three-step assistant: retrieve a policy, choose a tool and produce an answer. Add one retrieval miss and one tool timeout. Inspect whether a reviewer can follow the steps, locate the error and identify the prompt version without consulting a separate terminal log. Capture a reference outcome for every trial.
What should an evaluation protect?
Turn the two failures into regression cases. A revised prompt should address the original issue without expanding tool permissions or inventing a policy. Track the source passage, selected action and final answer as distinct checks. For a multi-turn conversation, verify that earlier context does not cause a later request to use the wrong customer or document.
What are the operational limits?
A trace is an observation, not a correctness guarantee. Missing instrumentation can leave gaps, and logging can expose sensitive content. Define redaction, project access and retention before broad ingestion. Keep evaluation datasets representative as the application changes; an old benchmark can remain green while new user tasks fail.
Which alternatives are relevant?
Compare Langfuse and Braintrust for overlapping tracing and evaluation work. Compare Helicone when request routing and usage monitoring are central. Use the same incident and retention requirements instead of comparing headline seat prices alone.
Sources checked October 27, 2026: Official documentation · Pricing and access conditions.