Skip to main content


The novel idea introduced in this template is the idea of using retrieval to select the set of tools to use to answer an agent query. This is useful when you have many many tools to select from. You cannot put the description of all the tools in the prompt (because of context length issues) so instead you dynamically select the N tools you do want to consider using at run time.

In this template we will create a somewhat contrived example. We will have one legitimate tool (search) and then 99 fake tools which are just nonsense. We will then add a step in the prompt template that takes the user input and retrieves tool relevant to the query.

This template is based on this Agent How-To.

Environment Setup​

The following environment variables need to be set:

Set the OPENAI_API_KEY environment variable to access the OpenAI models.

Set the TAVILY_API_KEY environment variable to access Tavily.


To use this package, you should first have the LangChain CLI installed:

pip install -U langchain-cli

To create a new LangChain project and install this as the only package, you can do:

langchain app new my-app --package openai-functions-tool-retrieval-agent

If you want to add this to an existing project, you can just run:

langchain app add openai-functions-tool-retrieval-agent

And add the following code to your file:

from openai_functions_tool_retrieval_agent import agent_executor as openai_functions_tool_retrieval_agent_chain

add_routes(app, openai_functions_tool_retrieval_agent_chain, path="/openai-functions-tool-retrieval-agent")

(Optional) Let's now configure LangSmith. LangSmith will help us trace, monitor and debug LangChain applications. You can sign up for LangSmith here. If you don't have access, you can skip this section

export LANGCHAIN_API_KEY=<your-api-key>
export LANGCHAIN_PROJECT=<your-project> # if not specified, defaults to "default"

If you are inside this directory, then you can spin up a LangServe instance directly by:

langchain serve

This will start the FastAPI app with a server is running locally at http://localhost:8000

We can see all templates at We can access the playground at

We can access the template from code with:

from langserve.client import RemoteRunnable

runnable = RemoteRunnable("http://localhost:8000/openai-functions-tool-retrieval-agent")

Help us out by providing feedback on this documentation page: