---
title: "Reranking"
description: "Reorder documents by relevance to a query using /v1/rerank."
icon: "book-open-cover"
---

Use reranking to sort documents by relevance for search, retrieval, and context selection.

## Provider Model Examples

- Cohere: `cohere/rerank-v3.5`
- vLLM: `vllm/BAAI/bge-reranker-v2-m3`
- Bedrock: `bedrock/<rerank-model-or-arn>`
- Vertex AI: `vertex/<ranking-model>`

## Basic Request

```bash
curl --location 'http://localhost:8080/v1/rerank' \
--header 'Content-Type: application/json' \
--data '{
  "model": "cohere/rerank-v3.5",
  "query": "What is Bifrost?",
  "documents": [
    {"text": "Bifrost is an AI gateway that unifies many LLM providers."},
    {"text": "Paris is the capital of France."},
    {"text": "Bifrost exposes an OpenAI-compatible API."}
  ]
}'
```

## Request Parameters

- `model` (required): model in `provider/model` format
- `query` (required): query used for ranking
- `documents` (required): array of documents with `text` (optional `id`, `meta`)
- `top_n` (optional): maximum number of results
- `max_tokens_per_doc` (optional): provider-dependent document token cap
- `priority` (optional): provider-dependent priority hint
- `return_documents` (optional): include matched document content in each result
- `fallbacks` (optional): fallback models in `provider/model` format

## Example with Options

```bash
curl --location 'http://localhost:8080/v1/rerank' \
--header 'Content-Type: application/json' \
--data '{
  "model": "cohere/rerank-v3.5",
  "query": "gateway observability",
  "top_n": 2,
  "return_documents": true,
  "documents": [
    {"id": "a", "text": "Bifrost supports observability plugins like OTEL and Maxim."},
    {"id": "b", "text": "Bifrost can run in Kubernetes and ECS."},
    {"id": "c", "text": "Token counting is available at /v1/responses/input_tokens."}
  ]
}'
```

## vLLM Endpoint Compatibility

When using a `vllm/...` model, Bifrost sends rerank requests to `/v1/rerank` first and automatically retries `/rerank` when the upstream endpoint responds with `404`, `405`, or `501`.

## Response Shape

```json
{
  "results": [
    {
      "index": 0,
      "relevance_score": 0.98,
      "document": {
        "id": "a",
        "text": "Bifrost supports observability plugins like OTEL and Maxim."
      }
    },
    {
      "index": 2,
      "relevance_score": 0.63,
      "document": {
        "id": "c",
        "text": "Token counting is available at /v1/responses/input_tokens."
      }
    }
  ],
  "model": "rerank-v3.5",
  "usage": {
    "prompt_tokens": 52,
    "completion_tokens": 0,
    "total_tokens": 52
  },
  "extra_fields": {
    "request_type": "rerank",
    "provider": "cohere",
    "latency": 245,
    "chunk_index": 0
  }
}
```

## Common Validation Errors

- Missing `query` -> `query is required for rerank`
- Empty `documents` -> `documents are required for rerank`
- Blank document text -> `document text is required for rerank at index N`
- `top_n < 1` -> `top_n must be at least 1`

## Next Steps

Now that you understand reranking, explore these related topics:

### Essential Topics

- **[Multimodal AI](./multimodal)** - Process images, audio, and multimedia content
- **[Tool Calling](./tool-calling)** - Enable AI models to use external tools and functions
- **[Provider Configuration](./provider-configuration)** - Multiple providers for redundancy
- **[Integrations](./integrations)** - Drop-in compatibility with existing SDKs

### Advanced Topics

- **[Core Features](../../features/)** - Advanced Bifrost capabilities
- **[Architecture](../../architecture/)** - How Bifrost works internally
- **[Deployment](../../deployment-guides)** - Production setup and scaling