diff --git a/google/downscoped/downscoping.go b/google/downscoped/downscoping.go
index 5d2ce6e..80677d4 100644
--- a/google/downscoped/downscoping.go
+++ b/google/downscoped/downscoping.go
@@ -1,28 +1,25 @@
 package downscoped
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"golang.org/x/oauth2"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"time"
 )
 
 const (
-	IDENTITY_BINDING_ENDPOINT = "https://sts.googleapis.com/v1beta/token"
+	identityBindingEndpoint = "https://sts.googleapis.com/v1beta/token"
 )
 
 // Defines an upper bound of permissions available for a GCP credential for one or more resources
 type AccessBoundary struct {
+	// One or more AccessBoundaryRules are required to define permissions for the new downscoped token
 	AccessBoundaryRules []AccessBoundaryRule `json:"accessBoundaryRules"`
 }
 
-func NewAccessBoundary() AccessBoundary {
-	return AccessBoundary{make([]AccessBoundaryRule, 0)}
-}
-
 type AvailabilityCondition struct {
 	Title       string `json:"title,omitempty"`
 	Expression  string `json:"expression"`
@@ -35,7 +32,7 @@ type AccessBoundaryRule struct {
 	Condition            *AvailabilityCondition `json:"availabilityCondition,omitempty"`
 }
 
-type DownScopedTokenResponse struct {
+type downscopedTokenResponse struct {
 	AccessToken     string `json:"access_token"`
 	IssuedTokenType string `json:"issued_token_type"`
 	TokenType       string `json:"token_type"`
@@ -47,12 +44,12 @@ type DownscopingConfig struct {
 	CredentialAccessBoundary AccessBoundary
 }
 
-func DownscopedTokenWithEndpoint(config DownscopingConfig, endpoint string) (oauth2.TokenSource, error) {
+func downscopedTokenWithEndpoint(ctx context.Context, config DownscopingConfig, endpoint string) (oauth2.TokenSource, error) {
 	if config.RootSource == nil {
-		return nil, fmt.Errorf("oauth2/google: rootTokenSource cannot be nil")
+		return nil, fmt.Errorf("oauth2/google/downscoped: rootTokenSource cannot be nil")
 	}
 	if len(config.CredentialAccessBoundary.AccessBoundaryRules) == 0 {
-		return nil, fmt.Errorf("oauth2/google: length of AccessBoundaryRules must be at least 1")
+		return nil, fmt.Errorf("oauth2/google/downscoped: length of AccessBoundaryRules must be at least 1")
 	}
 
 	downscopedOptions := struct {
@@ -63,12 +60,12 @@ func DownscopedTokenWithEndpoint(config DownscopingConfig, endpoint string) (oau
 
 	tok, err := config.RootSource.Token()
 	if err != nil {
-		return nil, fmt.Errorf("oauth2/google: unable to refresh root token %v", err)
+		return nil, fmt.Errorf("oauth2/google/downscoped: unable to refresh root token %v", err)
 	}
 
-	b, err := json.Marshal(downscopedOptions) // TODO: make sure that this marshals properly!
+	b, err := json.Marshal(downscopedOptions)
 	if err != nil {
-		return nil, fmt.Errorf("oauth2/google: Unable to marshall AccessBoundary payload %v", err)
+		return nil, fmt.Errorf("oauth2/google/downscoped: Unable to marshall AccessBoundary payload %v", err)
 	}
 
 	form := url.Values{}
@@ -78,19 +75,21 @@ func DownscopedTokenWithEndpoint(config DownscopingConfig, endpoint string) (oau
 	form.Add("subject_token", tok.AccessToken)
 	form.Add("options", url.QueryEscape(string(b)))
 
-	resp, err := http.PostForm(endpoint, form)
-	defer resp.Body.Close()
+	myClient := oauth2.NewClient(ctx, nil)
+	resp, err := myClient.PostForm(endpoint, form)
 	if err != nil {
 		return nil, fmt.Errorf("unable to generate POST Request %v", err)
 	}
+	defer resp.Body.Close()
 
-	if resp.StatusCode != http.StatusOK {
-		bodyBytes, _ := ioutil.ReadAll(resp.Body)
-		return nil, fmt.Errorf("unable to exchange token %v", string(bodyBytes))
+	var tresp downscopedTokenResponse
+	err = json.NewDecoder(resp.Body).Decode(&tresp)
+	if err != nil {
+		return nil, fmt.Errorf("unable to unmarshal response body: %v", err)
+	}
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("unable to exchange token %v", tresp)
 	}
-
-	tresp := DownScopedTokenResponse{}
-	json.NewDecoder(resp.Body).Decode(&tresp)
 
 	// an exchanged token that is derived from a service account (2LO) has an expired_in value
 	// a token derived from a users token (3LO) does not.
@@ -111,6 +110,6 @@ func DownscopedTokenWithEndpoint(config DownscopingConfig, endpoint string) (oau
 	return oauth2.StaticTokenSource(newToken), nil
 }
 
-func NewDownscopedTokenSource(config DownscopingConfig) (oauth2.TokenSource, error) {
-	return DownscopedTokenWithEndpoint(config, IDENTITY_BINDING_ENDPOINT)
+func NewDownscopedTokenSource(ctx context.Context, config DownscopingConfig) (oauth2.TokenSource, error) {
+	return downscopedTokenWithEndpoint(ctx, config, identityBindingEndpoint)
 }
diff --git a/google/downscoped/downscoping_test.go b/google/downscoped/downscoping_test.go
index fca1601..d25d2e0 100644
--- a/google/downscoped/downscoping_test.go
+++ b/google/downscoped/downscoping_test.go
@@ -1,6 +1,7 @@
 package downscoped
 
 import (
+	"context"
 	"golang.org/x/oauth2"
 	"io/ioutil"
 	"net/http"
@@ -14,7 +15,7 @@ var (
 )
 
 func Test_NewAccessBoundary(t *testing.T) {
-	got := NewAccessBoundary()
+	got := AccessBoundary{make([]AccessBoundaryRule, 0)}
 	want := AccessBoundary{nil}
 	if got.AccessBoundaryRules == nil || len(got.AccessBoundaryRules) != 0 {
 		t.Errorf("NewAccessBoundary() = %v; want %v", got, want)
@@ -26,7 +27,7 @@ func Test_DownscopedTokenSource(t *testing.T) {
 		if r.Method != "POST" {
 			t.Errorf("Unexpected request method, %v is found", r.Method)
 		}
-		if r.URL.String() != "/" { //TODO: Will this work, or do I need to redirect this to this test server instead?
+		if r.URL.String() != "/" {
 			t.Errorf("Unexpected request URL, %v is found", r.URL)
 		}
 		body, err := ioutil.ReadAll(r.Body)
@@ -40,11 +41,11 @@ func Test_DownscopedTokenSource(t *testing.T) {
 		w.Write([]byte(standardRespBody))
 
 	}))
-	new := NewAccessBoundary()
+	new := AccessBoundary{make([]AccessBoundaryRule, 0)}
 	new.AccessBoundaryRules = append(new.AccessBoundaryRules, AccessBoundaryRule{"test1", []string{"Perm1, perm2"}, nil})
 	myTok := oauth2.Token{AccessToken: "Mellon"}
 	tmpSrc := oauth2.StaticTokenSource(&myTok)
-	out, err := DownscopedTokenWithEndpoint(DownscopingConfig{tmpSrc, new}, ts.URL)
+	out, err := downscopedTokenWithEndpoint(context.Background(), DownscopingConfig{tmpSrc, new}, ts.URL)
 	if err != nil {
 		t.Fatalf("NewDownscopedTokenSource failed with error: %v", err)
 	}