#1Top Pick
Arize Phoenix
AI Observability🔴Developer
Phoenix is Arize's open-source LLM observability project, and it has quietly become the default way tens of thousands of teams see what their agents are actually doing in production. The pitch is simple: `pip install arize-phoenix`, instrument with OpenInference (or any OpenTelemetry-compatible library), and every LLM call, tool invocation, retrieval, and embedding shows up as a spanned timeline you can filter, search, and replay. No vendor account required, no proprietary SDK lock-in. The Open
Best for
Debugging why an agent's output went off the rails
Starting price
Free
Why it matched
Score 10
LLM Tracing & ObservabilityEvaluation FrameworkExperiment Management
Match reasons
- Primary category match: AI Observability
- Highest overall score and feature completeness
- Well-documented pros and cons
Tool CTA
Shortlist Arize Phoenix if you need a stronger fit for budget ai observability users around free and ai-observability.