> ## Documentation Index
> Fetch the complete documentation index at: https://docs.contextual.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Rerank

> Contextual AI How-to Guide

## Overview

Contextual AI's reranker is the first with instruction-following capabilities to handle conflicts in retrieval. It is the most accurate reranker in the world per industry-leading benchmarks like BEIR. To learn more about the reranker and its importance in RAG pipelines, please see our blog.

This how-to guide uses the same example to demonstrate how to use the reranker with the Contextual API directly, our Python SDK, and our Langchain package.

The current reranker models include:

* ctxl-rerank-v2-instruct-multilingual
* ctxl-rerank-v2-instruct-multilingual-mini
* ctxl-rerank-v1-instruct

## Global Variables & Examples

First, we will set up the global variables and examples we'll use with each different implementation method.

```python theme={null}
from google.colab import userdata

api_key = userdata.get("API_TOKEN")
base_url = "https://api.contextual.ai/v1"
rerank_api_endpoint = f"{base_url}/rerank"
```

```python theme={null}
query = "What is the current enterprise pricing for the RTX 5090 GPU for bulk orders?"

instruction = "Prioritize internal sales documents over market analysis reports. More recent documents should be weighted higher. Enterprise portal content supersedes distributor communications."

documents = [
    "Following detailed cost analysis and market research, we have implemented the following changes: AI training clusters will see a 15% uplift in raw compute performance, enterprise support packages are being restructured, and bulk procurement programs (100+ units) for the RTX 5090 Enterprise series will operate on a $2,899 baseline.",
    "Enterprise pricing for the RTX 5090 GPU bulk orders (100+ units) is currently set at $3,100-$3,300 per unit. This pricing for RTX 5090 enterprise bulk orders has been confirmed across all major distribution channels.",
    "RTX 5090 Enterprise GPU requires 450W TDP and 20% cooling overhead."
]

metadata = [
    "Date: January 15, 2025. Source: NVIDIA Enterprise Sales Portal. Classification: Internal Use Only",
    "TechAnalytics Research Group. 11/30/2023.",
    "January 25, 2025; NVIDIA Enterprise Sales Portal; Internal Use Only"
]

model = "ctxl-rerank-v2-instruct-multilingual"
```

## REST API implementation

```python theme={null}
import requests

headers = {
    "accept": "application/json",
    "content-type": "application/json",
    "authorization": f"Bearer {api_key}"
}
```

```python theme={null}
payload = {
    "query": query,
    "instruction": instruction,
    "documents": documents,
    "metadata": metadata,
    "model": model
}

rerank_response = requests.post(rerank_api_endpoint, json=payload, headers=headers)

print(rerank_response.json())
```

## Python SDK

```python theme={null}
try:
  from contextual import ContextualAI
except:
  %pip install contextual-client
  from contextual import ContextualAI

client = ContextualAI (api_key = api_key, base_url = base_url)
```

```python theme={null}
rerank_response = client.rerank.create(
    query = query,
    instruction = instruction,
    documents = documents,
    metadata = metadata,
    model = model
)

print(rerank_response.to_dict())
```

## Langchain

```python theme={null}
try:
  from langchain_contextual import ContextualRerank
except:
  %pip install langchain-contextual
  from langchain_contextual import ContextualRerank

from langchain_core.documents import Document
```

```python theme={null}
# intialize Contextual reranker via langchain_contextual
compressor = ContextualRerank(
    model=model,
    api_key=api_key,
)

# Prepare metadata in dictionary format for Langchain Document class
metadata_dict = [
    {
        "Date": "January 15, 2025",
        "Source": "NVIDIA Enterprise Sales Portal",
        "Classification": "Internal Use Only"
    },
    {
        "Date": "11/30/2023",
        "Source": "TechAnalytics Research Group"
    },
    {
        "Date": "January 25, 2025",
        "Source": "NVIDIA Enterprise Sales Portal",
        "Classification": "Internal Use Only"
    }
]


# prepare documents as langchain Document objects
# metadata stored in document objects will be extracted and used for reranking
langchain_documents = [
    Document(page_content=content, metadata=metadata_dict[i])
    for i, content in enumerate(documents)
]

# print to validate langchain document
print(langchain_documents[0])
```

```python theme={null}
# use compressor.compress_documents to rerank the documents
reranked_documents = compressor.compress_documents(
    query=query,
    instruction=instruction,
    documents=langchain_documents,
)
print(reranked_documents)
```

## Additional Resources

* [Read the blog post](https://contextual.ai/blog/introducing-instruction-following-reranker) to learn more about the Contextual AI Reranker
* [Access the related notebook](https://github.com/ContextualAI/examples/blob/main/03-standalone-api/03-rerank/rerank.ipynb) that demonstrates how to use the reranker with the Contextual API directly, our Python SDK, and our Langchain package
* [API Reference](/api-reference/rerank/rerank)
* [Python SDK](https://github.com/ContextualAI/contextual-client-python/blob/main/api.md#rerank)
* [Langchain Package](https://pypi.org/project/langchain-contextual/)