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

# Supported Parameters

> Request parameters accepted by the Auriko Chat Completions API

Auriko's `POST /v1/chat/completions` endpoint accepts the parameters below. The endpoint is OpenAI-compatible with Auriko-specific extensions for routing and metadata.

<Note>
  Not all providers support every optional parameter. Auriko drops unsupported ones and includes a warning in `routing_metadata.warnings`.
</Note>

To require full parameter support, set [`require_parameters`](/guides/advanced-routing#filter-by-parameter-support) to `true`. Check which parameters each provider supports via the [model directory endpoint](/api-reference/list-directory-models).

## Supported parameters

Auriko accepts and forwards 32 parameters to providers.

| Parameter               | Type            | Required    | Description                                                                                                       |
| ----------------------- | --------------- | ----------- | ----------------------------------------------------------------------------------------------------------------- |
| `extensions`            | Extensions      | No          |                                                                                                                   |
| `frequency_penalty`     | number          | No          | Frequency penalty (-2 to 2). Not supported by all providers.                                                      |
| `gateway`               | object          | Conditional | Auriko routing, metadata, and multi-model configuration. Omit for default single-model routing.                   |
| `logit_bias`            | object          | No          | Token logit bias. Not supported by all providers.                                                                 |
| `logprobs`              | boolean         | No          | Return log probabilities. Not supported by all providers.                                                         |
| `max_completion_tokens` | integer         | No          | Maximum tokens to generate. Reasoning models (o1/o3) use this field instead of `max_tokens`.                      |
| `max_tokens`            | integer         | No          | Maximum tokens to generate (legacy, use `max_completion_tokens`)                                                  |
| `messages`              | Message\[]      | Yes         | The messages to generate a completion for                                                                         |
| `min_p`                 | number          | No          | Min-P sampling. Supported by some vLLM providers.                                                                 |
| `model`                 | string          | Conditional | Model to route to, required for single-model requests.                                                            |
| `n`                     | integer         | No          | Number of completions to generate. Not supported by all providers.                                                |
| `parallel_tool_calls`   | boolean         | No          | Allow parallel tool calls                                                                                         |
| `presence_penalty`      | number          | No          | Presence penalty (-2 to 2). Not supported by all providers.                                                       |
| `prompt_cache_key`      | string          | No          | Prompt caching identifier. Supported by OpenAI.                                                                   |
| `reasoning_effort`      | string          | No          | Controls reasoning effort for supported models.                                                                   |
| `repetition_penalty`    | number          | No          | Repetition penalty. Supported by vLLM providers.                                                                  |
| `response_format`       | ResponseFormat  | No          |                                                                                                                   |
| `safety_identifier`     | string          | No          | Safety policy identifier. Supported by OpenAI.                                                                    |
| `seed`                  | integer         | No          | Random seed for reproducibility                                                                                   |
| `stop`                  | string \| array | No          | Stop sequences. Restrictions vary by provider and model.                                                          |
| `stream`                | boolean         | No          | Enable streaming responses                                                                                        |
| `stream_options`        | StreamOptions   | No          |                                                                                                                   |
| `temperature`           | number          | No          | Sampling temperature (0-2). Some providers restrict this value when reasoning is enabled.                         |
| `tool_choice`           | ToolChoice      | No          |                                                                                                                   |
| `tools`                 | Tool\[]         | No          | Tools the model can call                                                                                          |
| `top_a`                 | number          | No          | Top-A sampling. Supported by some vLLM providers.                                                                 |
| `top_k`                 | integer         | No          | Top-K sampling. Restricted by some providers when reasoning is enabled. Supported by Anthropic, Google, and vLLM. |
| `top_logprobs`          | integer         | No          | Number of top logprobs to return. Requires logprobs support.                                                      |
| `top_p`                 | number          | No          | Nucleus sampling parameter. Some providers restrict this value when reasoning is enabled.                         |
| `user`                  | string          | No          | User identifier for abuse detection                                                                               |
| `verbosity`             | string          | No          | Output verbosity control. Supported by OpenAI.                                                                    |
| `web_search_options`    | object          | No          | Web search configuration. Supported by OpenAI.                                                                    |

## Deprecated with auto-transform

These legacy OpenAI parameters are accepted and converted to their modern equivalents.

| Parameter       | Transforms To | Reason                                           |
| --------------- | ------------- | ------------------------------------------------ |
| `function_call` | `tool_choice` | deprecated by OpenAI, converted to `tool_choice` |
| `functions`     | `tools`       | deprecated by OpenAI, converted to `tools`       |

## Accepted and dropped

These parameters are accepted but not forwarded to providers. A warning is included in `routing_metadata.warnings`.

| Parameter      | Warning Message                                                          |
| -------------- | ------------------------------------------------------------------------ |
| `metadata`     | unsupported\_field: metadata                                             |
| `prediction`   | unsupported\_field: prediction                                           |
| `service_tier` | unsupported\_field: service\_tier (use gateway.routing.optimize instead) |
| `store`        | unsupported\_field: store                                                |

## Rejected with error

These parameters cause the request to fail with an error response.

| Parameter    | Status | Error Code               | Condition                    | Message                       |
| ------------ | ------ | ------------------------ | ---------------------------- | ----------------------------- |
| `audio`      | 400    | `unsupported_modalities` | always                       | audio output is not supported |
| `modalities` | 400    | `unsupported_modalities` | when requesting audio output | audio output is not supported |