Device api not working for the client credential

Hi,
I have been testing with the device list api by using this endpoint : https://api.spark.io/v1/devices
and Authorization: Basic Ykdid3i394k6kkd6332334b53h4hr== something like this header and it gives me 400 Bad request as

{
  "error": "invalid_request",
  "error_description": "Malformed auth header"
}

But if i try with the access token then it works well. Is it mandatory to use access token instead of header of credentials ?

Thanks

Hi,
Recently I am working on particle cloud api . I created a oauth client from a custom particle product and I was trying to use same for most of the api call and it worked in many endpoints too.

When i tried with https://api.spark.io/v1/devices it gives me error like:

{
  "error": "invalid_request",
  "error_description": "Malformed auth header"
}

I then tried with an access token parameter which I obtained from particle username and password, it worked . So is it a bug or limitation?

Thanks

I wanted to know if it is a bug or just a restriction to oauth client ?