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

# Model

> Reference for model classes and common parameters.

## Common Parameters

All model classes accept these parameters:

| Parameter               | Type    | Default           | Description                              |
| ----------------------- | ------- | ----------------- | ---------------------------------------- |
| `id`                    | `str`   | —                 | Model identifier (e.g., `"gpt-4o"`).     |
| `api_key`               | `str`   | env var           | API key. Defaults to provider's env var. |
| `base_url`              | `str`   | `None`            | Override API base URL.                   |
| `temperature`           | `float` | `None`            | Sampling temperature (0.0–2.0).          |
| `max_tokens`            | `int`   | `None`            | Max output tokens.                       |
| `top_p`                 | `float` | `None`            | Nucleus sampling.                        |
| `timeout`               | `float` | `None`            | Request timeout in seconds.              |
| `retries`               | `int`   | `0`               | Retry attempts.                          |
| `delay_between_retries` | `int`   | `1`               | Base retry delay in seconds.             |
| `exponential_backoff`   | `bool`  | `False`           | Exponential backoff for retries.         |
| `cache_response`        | `bool`  | `False`           | Cache responses locally.                 |
| `cache_ttl`             | `int`   | `3600`            | Cache TTL in seconds.                    |
| `cache_dir`             | `str`   | `".cache/models"` | Cache directory.                         |

## Methods

| Method                                                  | Returns                        | Description      |
| ------------------------------------------------------- | ------------------------------ | ---------------- |
| `invoke(messages, assistant_message, **kwargs)`         | `ModelResponse`                | Sync call.       |
| `ainvoke(messages, assistant_message, **kwargs)`        | `ModelResponse`                | Async call.      |
| `invoke_stream(messages, assistant_message, **kwargs)`  | `Iterator[ModelResponse]`      | Sync streaming.  |
| `ainvoke_stream(messages, assistant_message, **kwargs)` | `AsyncIterator[ModelResponse]` | Async streaming. |

## ModelResponse

| Field         | Type             | Description                    |
| ------------- | ---------------- | ------------------------------ |
| `content`     | `str`            | Response text.                 |
| `tool_calls`  | `List[ToolCall]` | Tool calls requested by model. |
| `usage`       | `Usage`          | Token usage metrics.           |
| `stop_reason` | `str`            | Why generation stopped.        |

## Provider Classes

| Import                                               | Provider   |
| ---------------------------------------------------- | ---------- |
| `from definable.model.openai import OpenAIChat`      | OpenAI     |
| `from definable.model.anthropic import Claude`       | Anthropic  |
| `from definable.model.google import Gemini`          | Google     |
| `from definable.model.deepseek import DeepSeekChat`  | DeepSeek   |
| `from definable.model.mistral import MistralChat`    | Mistral    |
| `from definable.model.moonshot import MoonshotChat`  | Moonshot   |
| `from definable.model.xai import xAI`                | xAI        |
| `from definable.model.perplexity import Perplexity`  | Perplexity |
| `from definable.model.ollama import Ollama`          | Ollama     |
| `from definable.model.openrouter import OpenRouter`  | OpenRouter |
| `from definable.model.openai_like import OpenAILike` | Custom     |

## String Shorthand

```python theme={null}
from definable.model.utils import resolve_model_string

model = resolve_model_string("openai/gpt-4o")
model = resolve_model_string("gpt-4o")  # defaults to OpenAI
```

Format: `"provider/model-id"` or bare `"model-id"` (defaults to OpenAI).