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

# Headers

> Request headers Nito reads and response headers it sets.

## Request

| Header | Notes |
| - | - |
| `Authorization` | Required for authenticated routes. Public model discovery needs no key. `Bearer <z_sk_ key>`. See [Authentication](/api/api-reference/overview/authentication). |
| `Content-Type` | `application/json`; `multipart/form-data` for chat requests that upload image files. |
| `X-Org-ID` | Optional with an API key. On authenticated routes, must be the UUID of the key's organization. Public model discovery ignores this header. |
| `X-Request-ID` | Caller-supplied trace ID, sanitized to 128 characters, echoed back. See [Request IDs](/api/api-reference/overview/request-ids). |
| `Idempotency-Key` | Validated as a UUID; not used to deduplicate. See [Safe retries](/api/features/safe-retries). |
| `nito-encrypted-*` | Envelope headers for Encrypted requests. See [Encrypted](/api/api-reference/chat-and-text/encrypted). |

## Response

| Header | Notes |
| - | - |
| `X-Request-ID` | Echoed from the request, or generated. |
| `X-RateLimit-Limit`, `X-RateLimit-Remaining`, `X-RateLimit-Reset` | The controlling request-rate bucket. `Reset` is UTC Unix epoch seconds. See [Rate limits](/api/api-reference/errors-and-rate-limits/rate-limits). |
| `Retry-After` | On over-limit `429` responses, when the wait is computable. |
| `Content-Type` | `application/json; charset=utf-8`, or `text/event-stream` for streams. |
| `Cache-Control` | `no-store` on inference, attestation, and public model discovery responses. |

The gateway also sets the standard security headers (`X-Content-Type-Options: nosniff`, `X-Frame-Options: DENY`, and `Strict-Transport-Security` on HTTPS deployments).

## Related

* [Request IDs](/api/api-reference/overview/request-ids)
* [Response format](/api/api-reference/overview/response-format)


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