Listed alphabetically. A tool is ranked by its reviews once it has 3.
| Tool | Reviews | Lowest paid plan | Free plan | Free trial | Public API | Runs on | Main features |
|---|---|---|---|---|---|---|---|
 BraintrustThe AI observability platform for tracing production, running evals, and catching regressions. | ReviewsNone yetWrite one for Braintrust | Lowest paid plan$249per monthPro, as of November 14, 2026 | Free planYes | Free trialNot confirmed | Public APINot confirmed | Runs onNot confirmed | Main features
|
 Confident AIThe AI quality platform for enterprise teams to standardize AI evals and observability across the org. | ReviewsNone yetWrite one for Confident AI | Lowest paid plan$200per organization per monthStarter, as of November 14, 2026 | Free planYes | Free trialNot confirmed | Public APIYes | ||
 LangfuseTrace, evaluate, and improve AI agents with one open platform. | ReviewsNone yetWrite one for Langfuse | Lowest paid plan$29per monthCore, as of November 14, 2026 | Free planYes | Free trialNot confirmed | Public APIYes | ||
 LangSmithComplete AI agent and LLM observability platform with tracing and real-time monitoring. | ReviewsNone yetWrite one for LangSmith | Lowest paid plan$39per seat per month, then pay as you goPlus, as of November 14, 2026 | Free planYes | Free trialNot confirmed | Public APINot confirmed | Runs onNot confirmed | |
 OpikAn end-to-end AI observability platform to test, ship, and improve agentic systems. | ReviewsNone yetWrite one for Opik | Lowest paid plan$19per monthPro Cloud, as of November 14, 2026 | Free planYes | Free trialYes | Public APIYes | ||
 PortkeyAI gateway and observability for AI teams. | ReviewsNone yetWrite one for Portkey | Lowest paid plan$49per monthProduction, as of November 14, 2026 | Free planYes | Free trialNot confirmed | Public APIYes | ||
 PromptLayerThe prompt CMS, eval harness, and observability stack for AI engineering teams. | ReviewsNone yetWrite one for PromptLayer | Lowest paid plan$49per monthPro, as of November 14, 2026 | Free planYes | Free trialNot confirmed | Public APIYes | ||
 TraceloopTraceloop turns evals and monitors into a continuous feedback loop so every release gets better. | ReviewsNone yetWrite one for Traceloop | Lowest paid planSee plans | Free planYes | Free trial14 days | Public APINot confirmed | Runs on |
From each tool's own website. “Not confirmed” means we couldn't confirm it there, not that the tool doesn't have it. Each tool's page says when its facts were checked.
How this list is made
A tool is listed here only when we've confirmed on its own website that it has a free plan. Tools we couldn't confirm it for are left out, even if they may have it. Vendors can't pay for a place on this list. Add a tool we missed