# Reasoning

> Ask the model to think before it answers, and read the reasoning it returns.


Each model lists the effort levels it accepts in `capabilities.reasoning_efforts` (see [Models](/en/getting-started/models)). More effort uses more output tokens, which are billed at the output rate. Leave the field out and the model uses its own default.

| API | Field |
|---|---|
| Chat completions | `reasoning_effort` |
| Responses | `reasoning.effort` |
| Messages | `thinking: {"type": "enabled", "budget_tokens": N}` or `{"type": "adaptive"}` with `output_config.effort` |

```python test
import os
from openai import OpenAI

client = OpenAI(base_url="https://api.notholy.com/v1", api_key=os.environ["NOTHOLY_API_KEY"])

r = client.chat.completions.create(
    model="notholy-specter",
    reasoning_effort="high",
    messages=[{"role": "user", "content": "Is a JWT signed with alg none ever acceptable? Answer in one line."}],
)
print(r.choices[0].message.content)
```

In chat completions and Responses, a level the model does not list returns `400 invalid_request`. Messages maps `thinking` and `output_config.effort` to the nearest level the model has: a budget of 16000 tokens or more is high, 4000 or more is medium, less is low, and `adaptive` is medium.

The reasoning text comes back as `reasoning_content` in chat completions, as `reasoning` items in Responses and as `thinking` blocks in Messages. When you send the conversation back, reasoning from earlier turns is dropped.

## Next

- [Cost practices](/en/guides/cost)