/oauth/request_token end point responds with payload that has content-type=text/html

[yellowSpasm]

I would like to get response from that enpoint as json encoded string. What I actually get in payload is this exact string:

‘oauth_token=ntZ19AAAAAAA0d0BAAABYMbMJzQ&oauth_token_secret=LeYCL6tutDItwod0pu7jljsWiWZUgsSR&oauth_callback_confirmed=true’

But is set to content-type= text/html ? In documentation it is said that responce format is in json. How can I get response as json encoded string? Tnx.