> For the complete documentation index, see [llms.txt](https://developer.ultimo.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.ultimo.net/api-key-templates/reservations/create-reservation.md).

# Create reservation

This workflow allows third parties to send a new reservation for a specific room with specified times.

The following parameters are used in the request. These are all required.

| **Parameter** | **Description**                                                                                                                                                                                        |
| ------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| ExternalId    | This is the Id used for the reservation in the system of the third party.                                                                                                                              |
| Description   | The description of the reservation for the room.                                                                                                                                                       |
| SpaceId       | This is the internal Ultimo Id of a room/space (entity).                                                                                                                                               |
| StartTime     | <p>The start time (datetime) of reservation.</p><p>Allowed formats:</p><ul><li>yyyy-MM-dd hh:mm:ss (i.e. 2018-08-21 15:21:59)</li><li>UTC: yyyy-MM-ddThh:mm:ssZ (i.e. 2018-08- 20T15:17:59Z)</li></ul> |
| EndTime       | <p>The end time (datetime) of reservation.</p><p>Allowed formats:</p><ul><li>yyyy-MM-dd hh:mm:ss (i.e. 2018-08-21 15:21:59)</li><li>UTC: yyyy-MM-ddThh:mm:ssZ (i.e. 2018-08- 20T15:17:59Z)</li></ul>   |
| ApplicantId   | The Id from the applicant of the reservation (entity employee in Ultimo).                                                                                                                              |

When these parameters are properly filled in, Ultimo will give a HTTP 200 response with the following properties:

| Parameter | Description                                                                |
| --------- | -------------------------------------------------------------------------- |
| UltimoId  | The internal Ultimo Id of a reservation for the room (ReservationLine Id). |

## Technical details

Basic URL (POST):

`https://customer.ultimo.com/api/V1/Action/REST_CreateReservation`

Header data:

| Parameter            | Description                                               |
| -------------------- | --------------------------------------------------------- |
| ApiKey               | Request an API key at (application manager or consultant) |
| ApplicationElementId | Fixed value “0167a94a-5dae-4efe-bf13-029a47728b97”        |

Body (example):

```csharp
{
    "ExternalId": "DEMO01",
    "Description": "Team meeting Front office",
    "SpaceId": "C-25",
    "StartTime": "2021-06-14 12:00:00",
    "EndTime": "2021-06-14 13:00:00",
    "Applicant": "ULTIMO"
}
```

### Normal response:

{% hint style="success" %}
Status: 200 OK
{% endhint %}

```csharp
{
    "Properties": {
        "UltimoId": "00000006712",
    }
}
```

### Response when the action is not allowed:

{% hint style="danger" %}
Status: 400 Bad Request
{% endhint %}

```csharp
{
    "message": "Room reservation cannot be requested or processed.\r\nCause: meeting room is not available.",
    "type": "3",
    "code": "1015"
}
```

In this case it is not allowed to make a reservation for a room that already has a reservation at the specified time. Ultimo will not process this action.

### Response when the API-key is invalid:

{% hint style="danger" %}
Status: 401 Unauthorized
{% endhint %}

```csharp
{
    "message": "Missing API key",
    "code": "MissingApiKey"
}
```


---

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