Prompt Chaining
Prompt chaining is a technique for solving complex tasks by breaking them into a sequence of smaller LLM calls, where the output of one prompt becomes the input to the next.
Definition
Prompt chaining is a technique for solving complex tasks by breaking them into a sequence of smaller LLM calls, where the output of one prompt becomes the input to the next.
Overview
Rather than asking a language model to complete a complicated, multi-step task in a single prompt, prompt chaining decomposes the task into discrete stages, each handled by its own prompt. For example, summarizing a long document, extracting key entities from the summary, and then drafting an email based on those entities could be three separate prompts chained together, with each step's output feeding the next step's input. This approach improves reliability because each sub-task is simpler and more constrained, making it easier for the model to follow instructions correctly and easier for developers to validate intermediate outputs. It also allows different steps to use different models, temperatures, or tools — a cheap, fast model might handle simple extraction while a more capable model handles the final synthesis. Prompt chains can include conditional branching, where the next prompt in the chain depends on the content of a prior output, and can incorporate external tool calls or retrieval steps between LLM calls. Prompt chaining is a foundational pattern behind more sophisticated agentic workflows and orchestration frameworks such as LangChain and LlamaIndex, which provide abstractions for composing these multi-step pipelines. It differs from chain-of-thought prompting, which elicits step-by-step reasoning within a single model call, whereas prompt chaining explicitly separates reasoning into multiple distinct calls with programmatic control in between. The trade-off is increased latency and cost from multiple API calls, along with added engineering complexity to manage state, error handling, and retries across the chain.
Key Concepts
- Decomposes a complex task into a sequence of simpler, focused LLM calls
- Passes the output of each step as input to the next
- Allows different models or parameters to be used at each stage
- Supports conditional branching based on intermediate outputs
- Enables validation and error handling between steps
- Can interleave tool calls or retrieval steps with LLM calls
- Improves reliability compared to a single monolithic prompt
- Forms the basis of many agent orchestration frameworks
Use Cases
Frequently Asked Questions
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