Glossary · AI & Agents
TruLens
Overview
What TruLens Is
TruLens is an open-source library for evaluating, tracking, and debugging LLM applications, including RAG systems and agents. It works through feedback functions, programmatic checks that score each response on quality dimensions. Its best-known set is the RAG triad: context relevance (did retrieval find the right material), groundedness (is the answer supported by that material), and answer relevance (does it address the question).
Evaluation Plus Observability
Beyond scoring, TruLens instruments your app so you can trace what happened inside each call, which chunks were retrieved, what the model saw, and where quality dropped. This observability makes it practical to compare experiments, spot regressions, and understand why a given answer scored poorly. That visibility is essential once an AI feature moves from demo to production.
How We Apply It
In our RAG development and knowledge assistant work, TruLens-style feedback functions and tracing help us prove a system works, not just hope it does. We measure the RAG triad across real queries while tuning retrieval and prompts. As a full-service, in-house team, we build evaluation into delivery so clients get AI features that hold up under real use.
Where we use it
Related Zen in Tech services
How our team puts TruLens to work in real projects.
FAQ
TruLens — common questions
What is the RAG triad in TruLens?
The RAG triad is three feedback metrics: context relevance (was the retrieved context appropriate), groundedness (is the answer supported by it), and answer relevance (does it address the query). Together they diagnose where a RAG pipeline fails.
Is TruLens free?
Yes. TruLens is open-source and free to use. As with other LLM-based evaluators, you pay for the model API calls used to run feedback functions.
TruLens vs Ragas?
Both evaluate RAG quality with LLM-based scoring. TruLens leans toward feedback functions plus tracing and observability for live apps, while Ragas focuses on batch metric evaluation over a test set. They complement each other well.
Need TruLens done right?
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