Short definition:
LCEL is a simple, readable syntax used inside LangChain to chain together AI actions — like prompting, calling APIs, searching files, or combining tools — in a clear, no-fuss format.
In Plain Terms
LCEL is like the scripting language behind the scenes when developers use LangChain to build AI-powered workflows. It helps define what happens step-by-step, such as:
“Take the user’s question → Look in the knowledge base → If not found, ask the language model → Return the final response.”
Instead of writing complex, custom code, LCEL lets teams build those chains of actions using a straightforward and standardized format.
Real-World Analogy
Imagine giving instructions to a smart assistant like this:
“First check the document, then use the calculator, then email the result.”
LCEL is how developers write those instructions for AI — just like recipe steps for a chef.
Why It Matters for Business
- Accelerates AI app development
LCEL reduces the complexity of building and maintaining logic chains behind AI-powered features. - Keeps workflows readable and testable
It’s easier for your dev team to audit, tweak, or scale AI workflows when the logic is written clearly — not buried in code. - Works across tools
Developers can combine memory, tools, APIs, and custom functions in one flow — ideal for automating internal tasks or building customer-facing agents.
Real Use Case
A support platform uses LCEL to:
- Search help center docs
- Ask GPT to rewrite the results in simpler terms
- Use an API to send that response via chatbot
All defined in a clean, readable chain using LCEL — so it’s easy to maintain as the product evolves.
Related Concepts
- LangChain (LCEL is part of the LangChain framework — it defines how workflows are built)
- AI Agents (LCEL helps specify how agents reason and act across steps)
- Chained Prompts / Multi-step Logic (What LCEL makes easy to implement)
- Function Calling (Can be triggered as one step in an LCEL chain)
- Composable AI(LCEL enables modular, building-block-style app development)
