Overview

Generate ranks of relevancy between the query and documents

A reranker evaluates the relevance between a query and a set of documents, and returns their ranked relevance scores. These documents are often the initial results obtained from an embedding‑based retrieval system, and the reranker refines their ordering to provide more accurate relevance assessments.

Unlike embedding models that encode queries and documents independently, rerankers are cross‑encoders that jointly process each query–document pair. This allows them to deliver more precise relevance predictions. As a result, it is common to apply a reranker to the top candidate documents retrieved through embedding‑based search or traditional lexical search methods such as BM25 or TF‑IDF.

Get Started

Example with Texts

In the example below, we use the Rerank API endpoint to index the list of documents from most to least relevant to the query "What is the capital of the United States?".

Request

In this example, the documents being passed in are a list of strings:

Python

import requests
import json

url = "https://llm.onerouter.pro/v1/rerank"
headers = {
    "Content-Type": "application/json",
    "Authorization": "Bearer {{API_KEY}}"
}
data = {
    "model": "qwen/qwen3-reranker-0.6b",
    "query": "What is the capital of the United States?",
    "top_n": 3,
    "documents": [
        "Carson City is the capital city of the American state of Nevada. At the 2010 United States Census, Carson City had a population of 55,274.",
        "The Commonwealth of the Northern Mariana Islands is a group of islands in the Pacific Ocean that are a political division controlled by the United States. Its capital is Saipan.",
        "Charlotte Amalie is the capital and largest city of the United States Virgin Islands. It has about 20,000 people. The city is on the island of Saint Thomas.",
        "Washington, D.C. (also known as simply Washington or D.C., and officially as the District of Columbia) is the capital of the United States. It is a federal district. The President of the USA and many major national government offices are in the territory. This makes it the political center of the United States of America.",
        "Capital punishment has existed in the United States since before the United States was a country. As of 2017, capital punishment is legal in 30 of the 50 states. The federal government (including the United States military) also uses capital punishment.",
    ]        
}

response = requests.post(url, headers=headers, data=json.dumps(data))

print(response.json())

cURL

Response

{
  "results": [
    {
      "index": 0,
      "relevance_score": 0.09358743578195572
    },
    {
      "index": 1,
      "relevance_score": 0.029959920793771744
    },
    {
      "index": 2,
      "relevance_score": 0.12215154618024826
    },
    {
      "index": 3,
      "relevance_score": 0.996448278427124
    },
    {
      "index": 4,
      "relevance_score": 0.00711569981649518
    }
  ],
  "usage": {
    "prompt_tokens": 632,
    "completion_tokens": 0,
    "total_tokens": 632
  }
}