Build a LangChain RAG Agent

Introduction

In this guide, we'll walk through how to create agents capable of answering questions based on any provided document using the Fetch.ai uagents and ai_engine libraries as well as openai and cohere. The aim is to assists you in building a LangChain Retrieval-Augmented Generation (RAG) Agent!

The process of creating RAG agents has been improved by offering a decentralized and modular framework through the uagents and ai_engine libraries. These tools streamline the integration of AI models like OpenAI and Cohere, enabling more efficient and scalable development of intelligent agents. With enhanced interoperability, security, and resource management, this framework allows developers to quickly build and deploy sophisticated agents that can effectively answer questions based on any provided document, making the entire process faster and more robust.

ℹ️

Check out the AI Engine package (opens in a new tab) and uAgents (opens in a new tab) packages to download them and start integrating this tools within your Agents project!

Current version of the AI Engine package is . Current version of the uAgents package is .

Let's dive into the LangChain RAG Agents development!

Prerequisites

Make sure you have read the following resources before going on with this guide:

API KEYs

Importantly, you will need two API keys to correctly go through this guide: one from OpenAI and one from Cohere. Follow the steps provided below to obtain these keys:

OpenAI API Key

Visit the OpenAI website (opens in a new tab).
Sign up or log in to your account.
Navigate to the API section.
Generate or retrieve your API key.

Cohere API Key

Visit the Cohere website (opens in a new tab).
Sign up or log in to your account.
Go to the API Keys section.
Copy an existing key or create a new one.: one from OpenAI and one from Cohere. Follow the steps below to obtain these keys.

Project structure and overview

Project structure

The project is structured as follows:

langchain-rag/
.
├── poetry.lock
├── pyproject.toml
└── src
    ├── agents
    │   ├── langchain_rag_agent.py
    │   └── langchain_rag_user.py
    ├── main.py
    └── messages
        └── requests.py

The source code directory (src) contains the following directories and files:

agents: Contains scripts for the LangChain agents.
- langchain_rag_agent.py: Script for the RAG agent (retrieves info, finds documents, generates answers).
- langchain_rag_user.py: Script for the User agent (asks questions, handles responses).
main.py: Starts both the RAG and user agents.
messages: Defines custom message models.
- requests.py: Defines the RagRequest message model (question, URL, optional deep read).

Environment variables

You'll need to set up environment variables for your project to run correctly. These variables include your API keys, which should be stored in a .env file within the src directory.

To do this, navigate to the src directory. Here, create and source the .env file. Within this one, add the following:

export COHERE_API_KEY="YOUR_COHERE_API_KEY"
export OPENAI_API_KEY="YOUR_OPENAI_API_KEY"

Langchain RAG setup

Project dependencies

You'll need several Python packages for the project. These can be managed efficiently using Poetry (opens in a new tab). The following dependencies are needed for the correct development of the Langchain RAG Agent project:

[tool.poetry.dependencies]
python = ">=3.10,<3.12"
uagents = "*"
requests = "^2.31.0"
langchain = "^0.2.11"
openai = "^1.12.0"
langchain-openai = "^0.1.19"
tiktoken = "^0.7.0"
cohere = "^4.47"
faiss-cpu = "^1.7.4"
validators = "^0.22.0"
uagents-ai-engine = "^0.4.0"
unstructured = "^0.12.4"

Messages Data Model

RagRequest Model

We now need to define the requests.py file under the messages folder in the project. Here, the RagRequest message data model represents the request to retrieve an answer to an user's question from a specified document URL. The script includes an optional parameter, deep_read, to determine if nested pages should also be read to retrieve the answer. This parameter is set to no as default.

The script look like the following:

requests.py

from typing import Optional
from uagents import Model, Field
 
 
class RagRequest(Model):
    question: str = Field(
        description="The question that the user wants to have an answer for."
    )
    url: str = Field(description="The url of the docs where the answer is.")
    deep_read: Optional[str] = Field(
        description="Specifies weather all nested pages referenced from the starting URL should be read or not. The value should be yes or no.",
        default="no",
    )

Here's a breakdown of the RagRequest message data Model:

question (str): This is the user's question that needs to be answered based on the provided website URL.
url (str): This is the URL of the website where the answer should be found.
deep_read (Optional[str], default="no"): This optional field allows you to specify whether the RAG agent should follow and read nested pages (i.e., pages linked from the starting URL). Valid values are "yes" or "no". By default, the agent focuses only on the initial URL.

Agents

LangChain RAG Agent

This step involves setting up the LangChain Retrieval-Augmented Generation (RAG) Agent which is able to scrape web content, retrieve relevant documents, and generate answers to user queries based on that content. Let's create the file within the agents directory we created under src directory of our project and name it langchain_rag_agent.py by using the following command: touch langchain_rag_agent.py

The agent is defined as a local agent with a Mailbox (opens in a new tab) and it is able to answer questions by fetching and summarizing information from a given website URL.

The script for this agent looks as follows:

langchain_rag_agent.py

import traceback
from uagents import Agent, Context, Protocol
import validators
from messages.requests import RagRequest
import os
from langchain_openai import ChatOpenAI
from langchain.prompts import ChatPromptTemplate
from langchain_community.document_loaders import UnstructuredURLLoader
import requests
from bs4 import BeautifulSoup
from urllib.parse import urlparse
from langchain_openai import OpenAIEmbeddings
from langchain_community.vectorstores import FAISS
from langchain.retrievers import ContextualCompressionRetriever
from langchain.retrievers.document_compressors import CohereRerank
from ai_engine import UAgentResponse, UAgentResponseType
import nltk
from uagents.setup import fund_agent_if_low
 
nltk.download("punkt")
nltk.download("averaged_perceptron_tagger")
 
 
LANGCHAIN_RAG_SEED = "YOUR_LANGCHAIN_RAG_SEED"
AGENT_MAILBOX_KEY = "YOUR_MAILBOX_KEY"
 
agent = Agent(
    name="langchain_rag_agent",
    seed=LANGCHAIN_RAG_SEED,
    mailbox=f"{AGENT_MAILBOX_KEY}@https://agentverse.ai",
)
 
fund_agent_if_low(agent.wallet.address())
 
docs_bot_protocol = Protocol("DocsBot")
 
 
PROMPT_TEMPLATE = """
Answer the question based only on the following context:
 
{context}
 
---
 
Answer the question based on the above context: {question}
"""
 
 
def create_retriever(
    ctx: Context, url: str, deep_read: bool
) -> ContextualCompressionRetriever:
    def scrape(site: str):
        if not validators.url(site):
            ctx.logger.info(f"Url {site} is not valid")
            return
 
        r = requests.get(site)
        soup = BeautifulSoup(r.text, "html.parser")
 
        parsed_url = urlparse(url)
        base_domain = parsed_url.scheme + "://" + parsed_url.netloc
 
        link_array = soup.find_all("a")
        for link in link_array:
            href: str = link.get("href", "")
            if len(href) == 0:
                continue
            current_site = f"{base_domain}{href}" if href.startswith("/") else href
            if (
                ".php" in current_site
                or "#" in current_site
                or not current_site.startswith(url)
                or current_site in urls
            ):
                continue
            urls.append(current_site)
            scrape(current_site)
 
    urls = [url]
    if deep_read:
        scrape(url)
        ctx.logger.info(f"After deep scraping - urls to parse: {urls}")
 
    try:
        loader = UnstructuredURLLoader(urls=urls)
        docs = loader.load_and_split()
        db = FAISS.from_documents(docs, OpenAIEmbeddings())
        compression_retriever = ContextualCompressionRetriever(
            base_compressor=CohereRerank(), base_retriever=db.as_retriever()
        )
        return compression_retriever
    except Exception as exc:
        ctx.logger.error(f"Error happened: {exc}")
        traceback.format_exception(exc)
 
 
@docs_bot_protocol.on_message(model=RagRequest, replies={UAgentResponse})
async def answer_question(ctx: Context, sender: str, msg: RagRequest):
    ctx.logger.info(f"Received message from {sender}, session: {ctx.session}")
    ctx.logger.info(
        f"input url: {msg.url}, question: {msg.question}, is deep scraping: {msg.deep_read}"
    )
 
    parsed_url = urlparse(msg.url)
    if not parsed_url.scheme or not parsed_url.netloc:
        ctx.logger.error("invalid input url")
        await ctx.send(
            sender,
            UAgentResponse(
                message="Input url is not valid",
                type=UAgentResponseType.FINAL,
            ),
        )
        return
    base_domain = parsed_url.scheme + "://" + parsed_url.netloc
    ctx.logger.info(f"Base domain: {base_domain}")
 
    retriever = create_retriever(ctx, url=msg.url, deep_read=msg.deep_read == "yes")
 
    compressed_docs = retriever.get_relevant_documents(msg.question)
    context_text = "\n\n---\n\n".join([doc.page_content for doc in compressed_docs])
    prompt_template = ChatPromptTemplate.from_template(PROMPT_TEMPLATE)
    prompt = prompt_template.format(context=context_text, question=msg.question)
 
    model = ChatOpenAI(model="gpt-4o-mini")
    response = model.predict(prompt)
    ctx.logger.info(f"Response: {response}")
    await ctx.send(
        sender, UAgentResponse(message=response, type=UAgentResponseType.FINAL)
    )
 
 
agent.include(docs_bot_protocol, publish_manifest=True)
 
 
if __name__ == "__main__":
    agent.run()

In order to correctly run this code, you need to provide the name, seed, mailbox, LANGCHAIN_RAG_SEED, PROMPT_TEMPLATE and AGENT_MAILBOX_KEY parameters to correctly run this example.

The agent fetches and processes information from specified URLs to answer users' questions. Let's explore the script above in more detail. Initially, multiple modules are imported, including tools for making HTTP requests, parsing HTML, and handling Natural Language Processing (NLP). The agent uses OpenAI's GPT-4o-mini model for generating answers based on retrieved documents. We then up an agent called langchain_rag_agent() with a unique seed and mailbox address. Check out the Mailbox guide for additional info on Agent Mailboxes.

To ensure the agent has sufficient funds to operate, the fund_agent_if_low() function is invoked.

Next, the DocsBot protocol is defined using the Protocol class of the uagents library to handle message interactions. This protocol uses a predefined prompt template to structure the questions and context for the language model.

The create_retriever() function is responsible for fetching and parsing web pages. If necessary, it can perform deep scraping, which involves gathering all linked pages within the same domain. The function validates URLs, retrieves HTML content, and uses BeautifulSoup to parse the HTML and find links. The documents are then loaded and split using LangChain's UnstructuredURLLoader, indexed with FAISS, and compressed with Cohere, creating a retriever that can extract relevant information.

The answer_question() function, decorated with the .on_message() handler , is triggered when the agent receives a message matching the RagRequest message data model. The function validates the input URL and creates a retriever to fetch relevant documents based on the question. The context alongside with the question are then used to create a prompt for the language model (ChatOpenAI), which generates the final answer.

The generated answer is then sent back to the user.

Finally, the agent is set to include the DocsBot protocol and is then run, which starts the agent and allows it to receive and process incoming messages.

LangChain User Agent

We are now ready to define the LangChain User Agent which interacts with the LangChain RAG agent defined previously to ask a question based on documents found at specified URLs. The user agent sends a request to the RAG agent to retrieve and process information from the web page and then handle the response. The agent is defined as a local agent with an endpoint (opens in a new tab).

The script looks as follows:

langchain_rag_user.py

from uagents import Agent, Context, Protocol
from messages.requests import RagRequest
from ai_engine import UAgentResponse
from uagents.setup import fund_agent_if_low
 
QUESTION = "How to install uagents using pip"
URL = "https://fetch.ai/docs/guides/agents/installing-uagent"
DEEP_READ = (
    "no"
)
 
RAG_AGENT_ADDRESS = "YOUR_LANGCHAIN_RAG_AGENT_ADDRESS"
 
user = Agent(
    name="langchain_rag_user",
    port=8000,
    endpoint=["http://127.0.0.1:8000/submit"],
)
fund_agent_if_low(user.wallet.address())
rag_user = Protocol("LangChain RAG user")
 
@rag_user.on_interval(60, messages=RagRequest)
async def ask_question(ctx: Context):
    ctx.logger.info(
        f"Asking RAG agent to answer {QUESTION} based on document located at {URL}, readin nested pages too: {DEEP_READ}"
    )
    await ctx.send(
        RAG_AGENT_ADDRESS, RagRequest(question=QUESTION, url=URL, deep_read=DEEP_READ)
    )
 
@rag_user.on_message(model=UAgentResponse)
async def handle_data(ctx: Context, sender: str, data: UAgentResponse):
    ctx.logger.info(f"Got response from RAG agent: {data.message}")
 
user.include(rag_user)
 
if __name__ == "__main__":
    rag_user.run()

Remember that you need to provide the QUESTION, URL, DEEP_READ, RAG_AGENT_ADDRESS, name, seed and endpoint parameters to correctly run this code.

Here, we have created the User Agent which interacts with the LangChain RAG Agent we previously defined. The User Agent periodically asks the RAG Agent a predefined question and then handles the response.

After importing all required modules and classes, a specific QUESTION is provided: "How to install uagents using pip". We also provide the URL for the webpage where the relevant information can be found to answer the question. The DEEP_READ variable is set to no thus indicating that the agent should only read the main page and not follow and read any nested or linked pages.

The RAG_AGENT_ADDRESS variable holds the address of the RAG agent, which is responsible for retrieving and processing the webpage content to answer the user's question.

We are now ready to define the User Agent. We create the langchain_rag_user is created with a specific port and endpoint, which is where it will communicate with the RAG Agent. The agent's wallet is funded if needed using the fund_agent_if_low() function.

We then proceed and define the protocol . A protocol named LangChain RAG user is defined using the Protocol class of the uagents library to handle the agent's interactions. This protocol contains two important functions:

The ask_question() function is decorated with the .on_interval() handler and it is set to run at 60-second intervals. This function sends a RagRequest message to the LangChain RAG agent, asking it to answer the QUESTION based on the specified URL. It then logs the QUESTION and URL details for debugging purposes.
The handle_data() function is decorated with the .on_message() handler and it handles incoming messages from the LangChain RAG agent. When a response is received, it logs the response message.

Finally, the LangChain RAG user protocol is then included using the .include() method into the agent which is then run by calling rag_user.run() in the main block.

Main script

We are now ready to define the main script for our project. In the src folder of our project we create a Python script named main.py using the following command: touch main.py

We then define the code within this one which looks like the one provided here below:

main.py

from uagents import Bureau
from agents.langchain_rag_agent import agent
from agents.langchain_rag_user import user
 
if __name__ == "__main__":
    bureau = Bureau(endpoint="http://127.0.0.1:8000/submit", port=8000)
    print(f"Adding RAG agent to Bureau: {agent.address}")
    bureau.add(agent)
    print(f"Adding user agent to Bureau: {user.address}")
    bureau.add(user)
    bureau.run()

Now, both of agents are set up and you will need to connect your local agents to the Agentverse so for them to be retrievable for communication and interaction with any other registered agent on the Fetch Network. This way, the langchain_rag_agent will be connected to the Agentverse using a Mailbox and afterward a Agent Function (opens in a new tab) will be created and registered (opens in a new tab) for this agent.

The langchain_rag_user agent is used as a testing agent for the RAG agent being registered on the Agentverse and made subsequently available on DeltaV for queries.

ℹ️

Head over to the following guide for a better understanding of local agent registration on the Agentverse.

Expected output

The expected output for this example should be similar to the following one where we questioned the RAG Agent with the question How to install uagents using pip from the RAG user agent:

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