Phoenix

Free tier

The open-source platform for AI agent development, tracing, and evaluation

Free tier available·Technical·Powered by Vendor Agnostic·API available·Open source

Key strengths

Full OpenTelemetry-native tracing for LLM agentsLLM-as-a-judge and human annotation for evaluationVendor-agnostic — works with any model, framework, or languageSelf-hostable with zero data leaving your infrastructureEnd-to-end iteration loop: trace → annotate → experiment → measure

Free tier + paid plans

Self-hostable

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Phoenix is built on OpenTelemetry standards and the OpenInference specification, providing native distributed tracing for LLM workflows without proprietary lock-in. It captures traces across multi-step agent pipelines, supports LLM-as-a-judge and human annotation for scalable evaluation, and provides a Prompt IDE and experiment runner for benchmarking prompt and retrieval changes. The platform can be deployed locally, via Docker, on Kubernetes with Helm, or as a managed cloud service, and integrates with coding agents via an MCP skill (npx skills add Arize-ai/phoenix).

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