When provided as a querystring param it’s client_id, not client-id.
Also, the documentation for the API reference is actually pretty good (some of the non-reference pages could use quite a bit of work), it’s just that you’re using the client id in a querystring param when all the examples for almost all endpoints show to use a header (and once v5 is removed and you need to use Helix, providing it in a header is the only way)