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

# Request headers

> Headers you can send with a request to the AI Gateway to use a saved prompt, steer the cache, keep content out of logs or set your own request reference.

None of these headers is required. Send them on any model request, in any format.

| Header | Value | What it does |
| - | - | - |
| `x-request-id` | Any text | Your own reference for the request. Altrum uses it instead of making one, returns it, and shows it in the [request log](/ai-gateway/request-logs). |
| `x-alt-prompt-id` | A prompt id | Puts a [saved prompt](/ai-gateway/prompts) before your messages. |
| `x-alt-prompt-version` | A whole number, such as `2` | The prompt version to use. Without it, the latest version. |
| `x-alt-cache-key` | Any text | Keeps this request's [cached](/ai-gateway/semantic-cache) answers apart from others, for example per customer. |
| `x-alt-cache-ttl` | `30s`, `5m`, `1h`, or seconds | Keeps the answer for less time than your cache setting. |
| `x-alt-cache-threshold` | `0` to `1` | Asks for a closer match than your cache setting. |
| `x-alt-cache-type` | `direct` or `semantic` | `direct` matches word for word only, `semantic` by meaning only. |
| `x-alt-cache-no-store` | `true` | Serves from the cache when it can, but does not store this answer. |
| `x-alt-disable-content-logging` | `true` | Keeps this request's prompt and reply out of the request log, even when your organization keeps content. |
| `x-alt-direct-key` | `true` | Sends your own provider key. See [Authentication](/api-reference/authentication#send-your-own-provider-key). |

The cache headers can only narrow what your organization set: a request cannot keep an answer longer, or accept a looser match, than the cache settings allow. In the same way, `x-alt-disable-content-logging` can only turn content logging off.

## Example

```bash theme={null}
curl https://api.altrum.ai/v1/chat/completions \
  -H "Authorization: Bearer $ALTRUM_VIRTUAL_KEY" \
  -H "Content-Type: application/json" \
  -H "x-request-id: order-4512-summary" \
  -H "x-alt-prompt-id: support-reply" \
  -H "x-alt-cache-key: customer-881" \
  -d '{"model": "openai/gpt-4o-mini", "messages": [{"role": "user", "content": "Where is my order?"}]}'
```

In an SDK, set them as default headers on the client, or per request: see [SDKs](/ai-gateway/sdks).


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