We recently Enabled Unity Catalog so using Account Level API and little stuck on a GET call. For some reason, just the GET call requires a User-Agent header while POST, PUT, PATCH.. all work without it. For workspace API, there was no need for User-Agent Header GET call, with Account Level API, getting 400.

So have to add this:  httpClient.DefaultRequestHeaders.Add("User-Agent", "PostmanRuntime/7.42.0");

var httpClient = _httpClientFactory.CreateClient("AdbClient");
var contentType = "application/scim+json";
httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue(contentType));
httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);

HttpResponseMessage response;

switch (httpMethod.Method)
{
    case "GET":
        // Only needed for Account Level API Call
        httpClient.DefaultRequestHeaders.Add("User-Agent", "PostmanRuntime/7.42.0");
        response = await httpClient.GetAsync(endpoint);
        break;
    case "POST":
        HttpContent postBody = new StringContent(contentBody);
        postBody.Headers.ContentType = new MediaTypeHeaderValue(contentType);
        response = await httpClient.PostAsync(endpoint, postBody);
        break;
    case "PUT":
        HttpContent putBody = new StringContent(contentBody);
        putBody.Headers.ContentType = new MediaTypeHeaderValue(contentType);
        response = await httpClient.PutAsync(endpoint, putBody);
        break;

Any reason for that?