Power Query - How to format options for Web.Content()?

Question

I am trying to access a web api which can return data in either JSON or XML. When connecting with Power Query I get a "400, Bad request" error though and I suspect it could be due to Power Query not explicitly providing accepted Content-Types
in the request. Anyone know how to add options to the Web.Content() request?
http://office.microsoft.com/en-001/excel-help/web-contents-HA104112310.aspx
Thanks!

Answer 1

I believe the default reponse content-type is JSON. It doesn't serve Power Query with anything but an error response though and with the help of Network Monitor I caught a bit more details (in Swedish).
Request:
Http: Request, GET /platsannons/matchning, Query:lanid=1
Command: GET
+ URI: /platsannons/matchning?lanid=1
ProtocolVersion: HTTP/1.1
Accept: */*
UserAgent: Mozilla/5.0 (compatible; Microsoft.Data.Mashup; http://go.microsoft.com/fwlink/?LinkID=304225)
Host: api.arbetsformedlingen.se
Accept-Encoding: gzip, deflate
Connection: Keep-Alive
HeaderEnd: CRLF
Response:
HTTPPayloadLine: {"Error":{"statuskod":400,"titel":"Bad Request","beskrivning":"Felaktig headerparameter: [Accept-Language]"}}
And the API can be found at:
http://api.arbetsformedlingen.se/
Would be great to be able to define custom headers to the request through options for cases like these. Thanks for the reply!
Best regards,
Daniel