# Sforce Call Options Header

Use the `Sforce-Call-Options` header to specify client-specific options when accessing Bulk API 2.0 resources.

## Header Field Name and Values

**Field name:** `Sforce-Call-Options`

**Field values:**

- `client`—A string that identifies a client, for use, for example, in event log files.
- `defaultNamespace`—A string that identifies a developer namespace prefix. Resolve field names in managed packages without having to specify the namespace everywhere.

**Example:**

If the developer namespace prefix is `battle`, and you have a custom field called `botId` in a package, set the default namespace with the call options header:

```nolang
Sforce-Call-Options: client=CaseSensitiveToken, defaultNamespace=battle
```

Then queries such as the following succeed:

```nolang
/services/data/vXX.X/query/?q=SELECT+Id+botID__c+FROM+Account
```

In this case, the actual field queried is the `battle__botId__c` field.

Using this header allows you to write client code without having to specify the namespace prefix. In the previous example, without the header you must write `battle__botId__c`.

If this field is set, and the query also specifies the namespace, the response doesn’t include the prefix. For example, if you set this header to `battle`, and issue a query like `SELECT+Id+battle__botID__c+FROM+Account`, the response uses a `botId__c` element, not a `battle_botId__c` element.

The `defaultNamespace` field is ignored when retrieving describe information, which avoids ambiguity between namespace prefixes and customer fields of the same name.