diff --git a/build.go b/build.go
index ad4a767..13adda2 100644
--- a/build.go
+++ b/build.go
@@ -49,7 +49,7 @@ func buildNode(v reflect.Value, typ NodeType, seenFlags map[string]bool) *Node {
 			name = strings.ToLower(dashedString(ft.Name))
 		}
 
-		tag := parseTag(fv, ft.Tag.Get("kong"))
+		tag := parseTag(fv, ft)
 
 		// Nested structs are either commands or args.
 		if ft.Type.Kind() == reflect.Struct && (tag.Cmd || tag.Arg) {
diff --git a/kong_test.go b/kong_test.go
index 7fbdbff..201615c 100644
--- a/kong_test.go
+++ b/kong_test.go
@@ -246,64 +246,6 @@ func TestMixedRequiredArgs(t *testing.T) {
 	})
 }
 
-func TestDefaultValueForOptionalArg(t *testing.T) {
-	var cli struct {
-		Arg string `kong:"arg,optional,default='👌'"`
-	}
-	p := mustNew(t, &cli)
-	_, err := p.Parse(nil)
-	require.NoError(t, err)
-	require.Equal(t, "👌", cli.Arg)
-}
-
-func TestNoValueInTag(t *testing.T) {
-	var cli struct {
-		Empty1 string `kong:"default"`
-		Empty2 string `kong:"default="`
-	}
-	p := mustNew(t, &cli)
-	_, err := p.Parse(nil)
-	require.NoError(t, err)
-	require.Equal(t, "", cli.Empty1)
-	require.Equal(t, "", cli.Empty2)
-}
-
-func TestCommaInQuotes(t *testing.T) {
-	var cli struct {
-		Numbers string `kong:"default='1,2'"`
-	}
-	p := mustNew(t, &cli)
-	_, err := p.Parse(nil)
-	require.NoError(t, err)
-	require.Equal(t, "1,2", cli.Numbers)
-}
-
-func TestBadString(t *testing.T) {
-	var cli struct {
-		Numbers string `kong:"default='yay'n"`
-	}
-	_, err := New(&cli)
-	require.Error(t, err)
-}
-
-func TestNoQuoteEnd(t *testing.T) {
-	var cli struct {
-		Numbers string `kong:"default='yay"`
-	}
-	_, err := New(&cli)
-	require.Error(t, err)
-}
-
-func TestEscapedQuote(t *testing.T) {
-	var cli struct {
-		DoYouKnow string `kong:"default='i don\\'t know'"`
-	}
-	p := mustNew(t, &cli)
-	_, err := p.Parse(nil)
-	require.NoError(t, err)
-	require.Equal(t, "i don't know", cli.DoYouKnow)
-}
-
 func TestInvalidDefaultErrors(t *testing.T) {
 	var cli struct {
 		Flag int `kong:"default='foo'"`
diff --git a/tag.go b/tag.go
index ed0d938..fe4f874 100644
--- a/tag.go
+++ b/tag.go
@@ -26,9 +26,15 @@ type Tag struct {
 	items map[string]string
 }
 
-func parseCSV(s string) map[string]string {
-	d := map[string]string{}
+type tagChars struct {
+	sep, quote, assign rune
+}
 
+var kongChars = tagChars{sep: ',', quote: '\'', assign: '='}
+var bareChars = tagChars{sep: ' ', quote: '"', assign: ':'}
+
+func parseCSV(s string, chr tagChars) map[string]string {
+	d := map[string]string{}
 	key := []rune{}
 	value := []rune{}
 	quotes := false
@@ -51,23 +57,23 @@ func parseCSV(s string) map[string]string {
 		} else {
 			eof = true
 		}
-		if !quotes && r == ',' {
+		if !quotes && r == chr.sep {
 			add()
 			continue
 		}
-		if r == '=' && inKey {
+		if r == chr.assign && inKey {
 			inKey = false
 			continue
 		}
 		if r == '\\' {
-			if next == '\'' {
+			if next == chr.quote {
 				idx++
-				r = '\''
+				r = chr.quote
 			}
-		} else if r == '\'' {
+		} else if r == chr.quote {
 			if quotes {
 				quotes = false
-				if next == ',' || eof {
+				if next == chr.sep || eof {
 					continue
 				}
 				fail("%v has an unexpected char at pos %v", s, idx)
@@ -91,7 +97,17 @@ func parseCSV(s string) map[string]string {
 	return d
 }
 
-func parseTag(fv reflect.Value, s string) *Tag {
+func getTagInfo(ft reflect.StructField) (string, tagChars) {
+	s, ok := ft.Tag.Lookup("kong")
+	if ok {
+		return s, kongChars
+	}
+
+	return string(ft.Tag), bareChars
+}
+
+func parseTag(fv reflect.Value, ft reflect.StructField) *Tag {
+	s, chars := getTagInfo(ft)
 	t := &Tag{
 		items: map[string]string{},
 	}
@@ -99,7 +115,7 @@ func parseTag(fv reflect.Value, s string) *Tag {
 		return t
 	}
 
-	t.items = parseCSV(s)
+	t.items = parseCSV(s, chars)
 
 	t.Cmd = t.Has("cmd")
 	t.Arg = t.Has("arg")
diff --git a/tag_test.go b/tag_test.go
new file mode 100644
index 0000000..1decec5
--- /dev/null
+++ b/tag_test.go
@@ -0,0 +1,95 @@
+package kong
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestDefaultValueForOptionalArg(t *testing.T) {
+	var cli struct {
+		Arg string `kong:"arg,optional,default='👌'"`
+	}
+	p := mustNew(t, &cli)
+	_, err := p.Parse(nil)
+	require.NoError(t, err)
+	require.Equal(t, "👌", cli.Arg)
+}
+
+func TestNoValueInTag(t *testing.T) {
+	var cli struct {
+		Empty1 string `kong:"default"`
+		Empty2 string `kong:"default="`
+	}
+	p := mustNew(t, &cli)
+	_, err := p.Parse(nil)
+	require.NoError(t, err)
+	require.Equal(t, "", cli.Empty1)
+	require.Equal(t, "", cli.Empty2)
+}
+
+func TestCommaInQuotes(t *testing.T) {
+	var cli struct {
+		Numbers string `kong:"default='1,2'"`
+	}
+	p := mustNew(t, &cli)
+	_, err := p.Parse(nil)
+	require.NoError(t, err)
+	require.Equal(t, "1,2", cli.Numbers)
+}
+
+func TestBadString(t *testing.T) {
+	var cli struct {
+		Numbers string `kong:"default='yay'n"`
+	}
+	_, err := New(&cli)
+	require.Error(t, err)
+}
+
+func TestNoQuoteEnd(t *testing.T) {
+	var cli struct {
+		Numbers string `kong:"default='yay"`
+	}
+	_, err := New(&cli)
+	require.Error(t, err)
+}
+
+func TestEscapedQuote(t *testing.T) {
+	var cli struct {
+		DoYouKnow string `kong:"default='i don\\'t know'"`
+	}
+	p := mustNew(t, &cli)
+	_, err := p.Parse(nil)
+	require.NoError(t, err)
+	require.Equal(t, "i don't know", cli.DoYouKnow)
+}
+
+func TestBareTags(t *testing.T) {
+	var cli struct {
+		Cmd struct {
+			Arg  string `arg`
+			Flag string `required default:"👌"`
+		} `cmd`
+	}
+
+	p := mustNew(t, &cli)
+	_, err := p.Parse([]string{"cmd", "arg", "--flag=hi"})
+	require.NoError(t, err)
+	require.Equal(t, "hi", cli.Cmd.Flag)
+	require.Equal(t, "arg", cli.Cmd.Arg)
+}
+
+func TestBareTagsWithJsonTag(t *testing.T) {
+	var cli struct {
+		Cmd struct {
+			Arg  string `json:"-" optional arg`
+			Flag string `json:"best_flag" default:"\"'👌'\""`
+		} `cmd json:"CMD"`
+	}
+
+	p := mustNew(t, &cli)
+	_, err := p.Parse([]string{"cmd"})
+	require.NoError(t, err)
+	require.Equal(t, "\"'👌'\"", cli.Cmd.Flag)
+	require.Equal(t, "", cli.Cmd.Arg)
+}