diff --git a/client_test.go b/client_test.go
index a1bbd07..d76a0eb 100644
--- a/client_test.go
+++ b/client_test.go
@@ -1,12 +1,16 @@
 package gcloudcx_test
 
 import (
+	"context"
+	"encoding/json"
 	"fmt"
 	"reflect"
 	"strings"
 	"testing"
 	"time"
 
+	"github.com/gildas/go-core"
+	"github.com/gildas/go-errors"
 	"github.com/gildas/go-gcloudcx"
 	"github.com/gildas/go-logger"
 	"github.com/google/uuid"
@@ -35,6 +39,7 @@ func (suite *ClientSuite) SetupSuite() {
 			Path:        fmt.Sprintf("./log/test-%s.log", strings.ToLower(suite.Name)),
 			Unbuffered:  true,
 			FilterLevel: logger.TRACE,
+			SourceInfo:  true,
 		},
 	).Child("test", "test")
 	suite.Logger.Infof("Suite Start: %s %s", suite.Name, strings.Repeat("=", 80-14-len(suite.Name)))
@@ -79,3 +84,92 @@ func (suite *ClientSuite) TestCanInitializeWithoutOptions() {
 	client := gcloudcx.NewClient(nil)
 	suite.Require().NotNil(client, "GCloudCX Client is nil")
 }
+
+func (suite *ClientSuite) TestClientNotFoundErrorShouldBeBadRequest() {
+	payload := `{"error":"invalid_client","description":"client not found","error_description":"client not found"}`
+	var apiError gcloudcx.APIError
+
+	err := json.Unmarshal([]byte(payload), &apiError)
+	suite.Require().NoError(err, "Unmarshalling should have succeeded")
+	suite.Logger.Errorf("Expected Error", apiError)
+	suite.Assert().ErrorIs(apiError, gcloudcx.BadCredentialsError)
+	suite.Assert().NotErrorIs(apiError, errors.RuntimeError)
+	suite.Assert().Equal(gcloudcx.BadCredentialsError.Status, apiError.Status)
+}
+
+func (suite *ClientSuite) TestAuthFailedErrorShouldBeBadRequest() {
+	payload := `{"error":"invalid_client","description":"authentication failed","error_description":"authentication failed"}`
+	var apiError gcloudcx.APIError
+
+	err := json.Unmarshal([]byte(payload), &apiError)
+	suite.Require().NoError(err, "Unmarshalling should have succeeded")
+	suite.Logger.Errorf("Expected Error", apiError)
+	suite.Assert().ErrorIs(apiError, gcloudcx.BadCredentialsError)
+	suite.Assert().NotErrorIs(apiError, errors.RuntimeError)
+	suite.Assert().Equal(gcloudcx.BadCredentialsError.Status, apiError.Status)
+}
+
+func (suite *ClientSuite) TestCanLoginWithClientCredentials() {
+	clientID := uuid.New()
+
+	if value := core.GetEnvAsString("PURECLOUD_CLIENTID", ""); len(value) > 0 {
+		clientID = uuid.MustParse(value)
+	}
+	
+	client := gcloudcx.NewClient(&gcloudcx.ClientOptions{
+		Region: core.GetEnvAsString("PURECLOUD_REGION", "mypurecloud.com"),
+		Logger: suite.Logger,
+	}).SetAuthorizationGrant(&gcloudcx.ClientCredentialsGrant{
+		ClientID: clientID,
+		Secret:   core.GetEnvAsString("PURECLOUD_CLIENTSECRET", "s3cr3t"),
+	})
+	err := client.Login(context.Background())
+	suite.Require().NoError(err, "Login should have succeeded")
+	suite.Require().NotEmpty(client.Grant.AccessToken(), "Access Token should not be empty")
+}
+
+func (suite *ClientSuite) TestShouldFailLoginWithInvalidClientCredentialsSecret() {
+	clientID := uuid.New()
+
+	if value := core.GetEnvAsString("PURECLOUD_CLIENTID", ""); len(value) > 0 {
+		clientID = uuid.MustParse(value)
+	}
+	
+	client := gcloudcx.NewClient(&gcloudcx.ClientOptions{
+		Region: core.GetEnvAsString("PURECLOUD_REGION", "mypurecloud.com"),
+		Logger: suite.Logger,
+	}).SetAuthorizationGrant(&gcloudcx.ClientCredentialsGrant{
+		ClientID: clientID,
+		Secret:   "s3cr3t",
+	})
+	err := client.Login(context.Background())
+	suite.Require().Error(err, "Login should have failed")
+	suite.Logger.Errorf("Expected Error", err)
+	suite.Assert().NotErrorIs(err, errors.RuntimeError)
+	suite.Assert().ErrorIs(err, gcloudcx.BadCredentialsError)
+
+	var apiError gcloudcx.APIError
+	suite.Require().ErrorAs(err, &apiError, "Error should be an APIError")
+	suite.Require().NotEmpty(apiError.MessageParams, "Error should have some parameters")
+	suite.Assert().Equal("authentication failed", apiError.MessageParams["description"])
+}
+
+func (suite *ClientSuite) TestShouldFailLoginWithInvalidClientCredentialsClientID() {
+	client := gcloudcx.NewClient(&gcloudcx.ClientOptions{
+		Region: core.GetEnvAsString("PURECLOUD_REGION", "mypurecloud.com"),
+		Logger: suite.Logger,
+	}).SetAuthorizationGrant(&gcloudcx.ClientCredentialsGrant{
+		ClientID: uuid.New(), // The chances of this being a valid Client ID are very low
+		Secret:   core.GetEnvAsString("PURECLOUD_CLIENTSECRET", "s3cr3t"),
+	})
+	err := client.Login(context.Background())
+	suite.Require().Error(err, "Login should have failed")
+	suite.Logger.Errorf("Expected Error", err)
+	suite.Assert().NotErrorIs(err, errors.RuntimeError)
+	suite.Assert().ErrorIs(err, gcloudcx.BadCredentialsError)
+
+	var apiError gcloudcx.APIError
+	suite.Require().ErrorAs(err, &apiError, "Error should be an APIError")
+	suite.Require().NotEmpty(apiError.MessageParams, "Error should have some parameters")
+	suite.Assert().Equal("client not found", apiError.MessageParams["description"])
+}
diff --git a/error.go b/error.go
index ba1071e..61d0349 100644
--- a/error.go
+++ b/error.go
@@ -38,7 +38,7 @@ var (
 	// AuthenticationRequiredError means the request should authenticate first
 	AuthenticationRequiredError = APIError{Status: 401, Code: "authentication.required", Message: "No authentication bearer token specified in authorization header."}
 	// BadCredentialsError means the credentials are invalid
-	BadCredentialsError = APIError{Status: 401, Code: "bad.credentials", Message: "Invalid login credentials."}
+	BadCredentialsError = APIError{Status: 401, Code: "bad.credentials", Message: "Invalid login credentials (%s)."}
 	// CredentialsExpiredError means the credentials are expired
 	CredentialsExpiredError = APIError{Status: 401, Code: "credentials.expired", Message: "The supplied credentials are expired and cannot be used."}
 
@@ -138,6 +138,16 @@ func (e APIError) As(target interface{}) bool {
 	return false
 }
 
+// With creates a new Error from a given sentinel telling "what" is wrong and eventually their value.
+//
+// With also records the stack trace at the point it was called.
+func (e APIError) With(what string, values ...interface{}) error {
+	final := e
+	final.MessageWithParams = fmt.Sprintf(final.Message, what)
+	final.Stack.Initialize()
+	return final
+}
+
 // WithStack creates a new error from a given Error and records its stack.
 func (e APIError) WithStack() error {
 	final := e
@@ -154,9 +164,20 @@ func (e *APIError) UnmarshalJSON(payload []byte) (err error) {
 	}{}
 	err = json.Unmarshal(payload, &oauthError)
 	if err == nil && len(oauthError.Error) > 0 && len(oauthError.Description) > 0 {
-		*e = APIError{
-			Code:    BadCredentialsError.Code,
-			Message: fmt.Sprintf("%s: %s", oauthError.Description, oauthError.Error),
+		switch oauthError.Error {
+		case "invalid_client":
+			*e = BadCredentialsError
+			e.Message = fmt.Sprintf(e.Message, oauthError.Description)
+			e.MessageParams = map[string]string{
+				"reason": oauthError.Error,
+				"description": oauthError.Description,
+			}
+		default:
+			*e = APIError{
+				Status:  BadCredentialsError.Status,
+				Code:    BadCredentialsError.Code,
+				Message: fmt.Sprintf("%s: %s", oauthError.Description, oauthError.Error),
+			}
 		}
 		return nil
 	}
diff --git a/request.go b/request.go
index 4dc9381..2322eba 100644
--- a/request.go
+++ b/request.go
@@ -83,7 +83,7 @@ func (client *Client) SendRequest(context context.Context, path URI, options *re
 	correlationID := ""
 	if res != nil {
 		correlationID = res.Headers.Get("Inin-Correlation-Id")
-		log = log.Record("correlationId", correlationID)
+		log = log.Record("gcloudcx-correlationId", correlationID)
 	}
 	if err != nil {
 		urlError := &url.Error{}
@@ -119,9 +119,9 @@ func (client *Client) SendRequest(context context.Context, path URI, options *re
 				apiError.Status = errors.HTTPUnauthorized.Code
 				apiError.Code = errors.HTTPUnauthorized.ID
 			}
-			return errors.WithStack(apiError)
+			return apiError.WithStack()
 		}
-		return err
+		return errors.WithStack(err)
 	}
 	log.Debugf("Successfuly sent request in %s", duration)
 	return nil
diff --git a/version.go b/version.go
index a127c8f..9379251 100644
--- a/version.go
+++ b/version.go
@@ -4,7 +4,7 @@ package gcloudcx
 var commit string
 
 // VERSION is the version of this application
-var VERSION = "0.7.15" + commit
+var VERSION = "0.7.16" + commit
 
 // APP is the name of the application
 const APP string = "GCloudCX Client"