Client registration fails

I can’t get client registration to work from a REST POST.
For auth I use an initial access token created in the realm and included as a bearer auth token in the request.
Endpoint is like this: http://keycloak.server/auth/realms/realm/clients-registrations/openid-connect

JSON payload:

“client_name” : “sample”


Response is 401 Unauthorized:

"error": "invalid_token",

"error_description": "Failed decode token"


It seems to not like the token.