rerank

To use, you should have langchain_ibm python package installed, and the environment variable WATSONX_API_KEY set with your API key, or pass it as a named parameter api_key to the constructor.

pip install -U langchain-ibm

# or using uv
uv add langchain-ibm

export WATSONX_API_KEY="your-api-key"

from langchain_ibm import WatsonxRerank
from ibm_watsonx_ai.foundation_models.schema import RerankParameters

parameters = RerankParameters(truncate_input_tokens=20)

ranker = WatsonxRerank(
    model_id="cross-encoder/ms-marco-minilm-l-12-v2",
    url="https://us-south.ml.cloud.ibm.com",
    project_id="*****",
    params=parameters,
    # api_key="*****"
)

query = "red cat chasing a laser pointer"
documents = [
    "A red cat darts across the living room, pouncing on a red laser dot.",
    "Two dogs play fetch in the park with a tennis ball.",
    "The tabby cat naps on a sunny windowsill all afternoon.",
    "A recipe for tuna casserole with crispy breadcrumbs.",
]

ranker.rerank(documents=documents, query=query)

[
    {"index": 0, "relevance_score": 0.8719543218612671},
    {"index": 2, "relevance_score": 0.6520894169807434},
    {"index": 1, "relevance_score": 0.6270776391029358},
    {"index": 3, "relevance_score": 0.4607713520526886},
]