Every option in the catalog for when you need to trace, score and debug what your AI app actually did — 5 LLM evaluation and observability tools, 5 of them free or freemium, with the pricing tier printed on every row.
Flocci AI Tools lists 5 of them, ordered free tiers first: Arize Phoenix, Braintrust, Langfuse, Promptfoo and W&B Weave. Every one of them is free or has a free tier. Each entry states what it uniquely does rather than a score.
1 on this page are marked fully free with no paid plan at all: Arize Phoenix. The remaining 4 are freemium, trial or paid, and each is labelled with its exact tier so nothing surprises you at sign-up.
Free tools first, then freemium, then trial, then paid, and alphabetically inside each tier. Nobody pays to appear higher: Flocci AI Tools carries no ads, no sponsored slots and no paid listings, so the order reflects price and nothing else.
| Tool | Pricing | Type | Listed for |
|---|---|---|---|
| Arize Phoenix | Free | LLM Eval & Observability | Fully open-source, self-hostable with zero setup via `uvx` (pip/conda also supported) |
| Braintrust | Freemium | LLM Eval & Observability | Free Starter plan ships model credits and scored evals with no card required |
| Langfuse | Freemium | LLM Eval & Observability | Fully open-source and self-hostable for free via Docker Compose/Kubernetes, not just a hosted SaaS |
| Promptfoo | Freemium | LLM Eval & Observability | Open-source CLI/library for evaluating prompts, models and RAG pipelines side by side, runs in CI |
| W&B Weave | Freemium | LLM Eval & Observability | Agent-native tracing model with sessions, steps, tools and sub-agents as first-class concepts (not generic spans) |