LlamaIndex Expert Skill
LlamaIndex is an MIT-licensed Python framework for building LLM applications over your data. In 2026, it has evolved from a RAG indexing library into an event-driven workflow framework with integrated production runtime (llama-deploy), agent orchestration (AgentWorkflow), knowledge graph construction (PropertyGraphIndex), and OpenTelemetry-native observability.
The framework is organized around seven core primitives: Reader (data loaders), Document/Node (chunked content model), Index (data structures over Nodes), Retriever (relevant Node selection), Query Engine (retriever + synthesis), Agent (LLM with tools), and Workflow (event-driven orchestration).
Key Principles
These principles govern every decision when building with LlamaIndex. Read them before proceeding to the reference guides.
- Decouple retrieval chunks from synthesis chunks. The embedding representation that retrieves well differs from the context representation that generates well. Use
SentenceWindowNodeParser + MetadataReplacementNodePostProcessor for this pattern.
- Rerank before you generate. Hybrid retrieval + reranker is the minimum viable production RAG configuration.
- Agents are Workflows.
FunctionAgent and AgentWorkflow are pre-configured Workflows. Drop to raw Workflow when you need custom control flow.
- Graphs are not just vector stores.
PropertyGraphIndex adds structural path traversal that vector similarity cannot provide — combine both for maximum retrieval quality.
- Evaluate in the same process. Span-attached evaluation preserves the connection between the output and the retrieval context that produced it.
Where to Start
The pipeline has 9 phases from Ingest to Deploy. If you're joining mid-stream with existing work, find your entry point:
Pipeline Mode
Different tasks need different levels of rigor. Match your scope to a mode:
Rule of thumb: if you're shipping to users, run Full mode. If you're exploring, run Quick. If you're measuring, run Evaluate.
Quick Reference
When to Use This Skill
Load this skill any time you are:
- Building a RAG pipeline over enterprise or personal data
- Comparing LlamaIndex with LangChain, Haystack, or DSPy
- Designing multi-agent systems with handoff between specialist agents
- Deploying an LLM application to production with observability
- Constructing knowledge graphs from unstructured documents
- Debugging common LlamaIndex failures (retrieval miss, handoff bug, async issues)
When NOT to Use LlamaIndex — Framework Routing Guide
This skill is part of a portfolio of framework skills. When deciding which framework fits, use this routing table: