Rerank API

POST /api/v1/rerank — score how relevant each document is to a query. Cohere-compatible request and response.

Score how relevant each document is to a query, then sort them. Use it as a second stage after vector or keyword search: fetch 50–100 candidates, rerank, and keep the top few. The body is compatible with Cohere's Rerank API.

Authenticate with an LLM API key (sk-ar-v1-…) from /dashboard/keys, sent as Authorization: Bearer …. Management keys (ak_…) are not accepted.

Request

Field	Type	Required	Description
`model`	string	yes	A rerank model id, e.g. `cohere/rerank-v3.5`. See Models.
`query`	string	yes	The search query.
`documents`	(string \| `{text: string}`)[]	yes	Up to 1,000 documents to score.
`top_n`	integer (≥ 1)	no	Return only the best `top_n` results. Defaults to all documents.
`return_documents`	boolean	no	When `true`, each result includes `document.text`. Defaults to `false`.
`max_tokens_per_doc`	integer (≥ 1)	no	Truncate each document to this many tokens before scoring.
`session_id`	string	no	Groups related requests in Request Logs.

curl https://anyrouter.dev/api/v1/rerank \
  -H "Authorization: Bearer $ANYROUTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "cohere/rerank-v3.5",
    "query": "What is the capital of France?",
    "documents": [
      "Paris is the capital and largest city of France.",
      "Berlin is the capital of Germany.",
      "Bananas are rich in potassium."
    ],
    "top_n": 2
  }'

Response

{
  "id": "162b4aa9-d997-4942-896a-ef65644ff544",
  "model": "cohere/rerank-v3.5",
  "results": [
    { "index": 0, "relevance_score": 0.892 },
    { "index": 1, "relevance_score": 0.073 }
  ],
  "usage": {
    "prompt_tokens": 1000,
    "total_tokens": 1000,
    "search_units": 1,
    "cost": 0.002
  }
}

Field	Type	Description
`id`	string	Response id.
`model`	string	The model id you requested.
`results[]`	array	Sorted by `relevance_score`, highest first.
`results[].index`	integer	Position of the document in your `documents` array.
`results[].relevance_score`	number	Relevance between 0 and 1. Compare scores within one request, not across models.
`results[].document`	`{text}`	Present only when `return_documents` is `true`.
`usage.prompt_tokens`	integer	Billed tokens (see Pricing).
`usage.search_units`	integer	Provider search units, when the provider reports them.
`usage.cost`	number	USD charged for this request.

Pricing

Rerank models are priced per 1M input tokens, like the rest of the catalog. AnyRouter counts tokens over the query plus every document (about 4 characters per token), because rerank providers do not return token counts. Each provider search unit (one query with up to 100 documents) bills at least 1,000 tokens, so a very small request costs the same as one search.

Requests with your own Cohere key (BYOK) are not charged by AnyRouter.

Models

Rerank models appear under the Rerank tab at anyrouter.dev/models. Sending a chat or embedding model to this endpoint returns 400 model_not_rerank_compatible.

Errors

Status	Code	When
400	`missing_required_fields`	`model`, `query`, or `documents` is missing.
400	`invalid_request`	A document is not a string or `{text}`, `top_n` is not a positive integer, or there are more than 1,000 documents.
400	`model_not_rerank_compatible`	The model is not a rerank model.
404	`model_unavailable`	No route serves the model for your key.
502	`upstream_error`	Every provider for the model failed.