Response Synthesizer


A Response Synthesizer is what generates a response from an LLM, using a user query and a given set of text chunks. The output of a response synthesizer is a Response object.

The method for doing this can take many forms, from as simple as iterating over text chunks, to as complex as building a tree. The main idea here is to simplify the process of generating a response using an LLM across your data.

When used in a query engine, the response synthesizer is used after nodes are retrieved from a retriever, and after any node-postprocessors are ran.


Confused about where response synthesizer fits in the pipeline? Read the high-level concepts

Usage Pattern

Use a response synthesizer on it’s own:

from llama_index.schema import Node
from llama_index.response_synthesizers import ResponseMode, get_response_synthesizer

response_synthesizer = get_response_synthesizer(response_mode=ResponseMode.COMPACT)

response = response_synthesizer.synthesize("query text", nodes=[Node(text="text"), ...])

Or in a query engine after you’ve created an index:

query_engine = index.as_query_engine(response_synthesizer=response_synthesizer)
response = query_engine.query("query_text")

You can find more details on all available response synthesizers, modes, and how to build your own below.


Below you can find detailed API information for each response synthesis module.