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

# Budget Routing

> Set a cost ceiling per request and get the best model within it.

Pass `budget_cents` to automatically select the highest-quality model that fits within your cost limit. This overrides the `model` parameter.

## Request

```json theme={null}
{
  "budget_cents": 0.5,
  "messages": [{"role": "user", "content": "Translate to Spanish: Hello world"}],
  "include_routing": true
}
```

## Response

```json theme={null}
{
  "model": "deepseek-v3",
  "routing": {
    "budget_routing": {
      "requested_budget_cents": 0.5,
      "resolved": "deepseek-v3",
      "reason": "Best model within 0.5¢: DeepSeek V3 (0.3¢/req)"
    }
  },
  "cost": {"this_request": "$0.003"}
}
```

## Parameters

| Parameter         | Type    | Description                                                |
| ----------------- | ------- | ---------------------------------------------------------- |
| `budget_cents`    | number  | Maximum cost in cents for this request. Overrides `model`. |
| `include_routing` | boolean | Include the routing decision in the response.              |

## Code examples

<CodeGroup>
  ```python Python theme={null}
  import requests, os

  r = requests.post("https://www.ninjachat.ai/api/v1/chat",
      headers={"Authorization": f"Bearer {os.environ['NINJACHAT_API_KEY']}"},
      json={
          "budget_cents": 1.0,
          "messages": [{"role": "user", "content": "Explain gradient descent"}],
          "include_routing": True,
      }
  )
  data = r.json()
  print(f"Model: {data['model']}, Cost: {data['cost']['this_request']}")
  ```

  ```bash cURL theme={null}
  curl -X POST https://www.ninjachat.ai/api/v1/chat \
    -H "Authorization: Bearer nj_sk_YOUR_API_KEY" \
    -H "Content-Type: application/json" \
    -d '{
      "budget_cents": 0.5,
      "messages": [{"role": "user", "content": "What is 2+2?"}],
      "include_routing": true
    }'
  ```
</CodeGroup>

Budget routing works alongside [smart routing](/smart-routing) — if you pass both `model: "auto"` and `budget_cents`, the budget ceiling takes priority.