Auto Evaluator
FreeLangchain auto evaluator 
FreeFree tier
About Auto Evaluator
Auto Evaluator is an open-source tool built by LangChain that systematically evaluates the quality of LLM-based question-answering systems. It addresses the challenge of inconsistent QA performance by auto-generating test sets from documents and using model-graded evaluation to assess answer relevance and similarity to ground truth. Users can configure QA chain components (e.g., retriever, LLM) and run experiments to compare results, with a table summarizing performance. The app offers both a demo mode (pre-loaded data) and a playground mode for custom documents and test sets.
Key Features
Auto-generates QA test sets from input documents using LangChain's QAGenerationChain
Model-graded evaluation of retrieved document relevance and answer similarity to ground truth
Configurable QA chains with choice of retriever, LLM, and chunk parameters
Supports both demo mode (pre-loaded data) and playground mode (custom documents and test sets)
Outputs a results table summarizing questions, expected answers, and evaluation scores
Pros & Cons
Pros
- Systematic and repeatable evaluation methodology combining auto-generated test sets with model-graded scoring
- Reduces manual effort by automating both test set creation and evaluation
- Flexible configuration allows users to experiment with different components (retrievers, LLMs, prompts)
- Open source and free to use, with code available on GitHub
Cons
- Repository is archived and read-only as of 2024 (no longer actively maintained by LangChain)
- Requires technical setup and familiarity with LangChain to run locally
- Model-graded evaluation quality depends on the grading LLM and prompt selection, which may introduce bias
- Demo doc set is limited to a single podcast transcript; users must supply their own documents for custom use
Best For
Evaluating and comparing different QA chain configurations (e.g., chunk size, retriever, model)Detecting hallucination or poor answer quality in retrieval-augmented generation systemsBenchmarking LLM-based QA performance on domain-specific documentsRapidly prototyping and iterating on QA pipelines with systematic feedback
FAQ
What is Auto Evaluator?
Auto Evaluator is an open-source app from LangChain that helps evaluate the quality of LLM-based question-answering systems. It auto-generates a test set of question-answer pairs from documents and then grades the QA system's answers using model-graded evaluation.
How does the evaluation work?
The app uses two model-graded prompts: one to evaluate the relevance of retrieved documents to the question, and another to evaluate the similarity of the generated answer to the ground truth answer. Users can select which grading prompts to use.
Can I use my own documents and test set?
Yes, the playground mode allows you to input your own documents. You can optionally provide your own test set of question-answer pairs; if not supplied, the app will auto-generate one. If the provided test set is smaller than the desired number of questions, the app will auto-generate the remainder.