diff --git a/cmd/protoc-gen-doc/flags.go b/cmd/protoc-gen-doc/flags.go
index 40aa8976..90d54c94 100644
--- a/cmd/protoc-gen-doc/flags.go
+++ b/cmd/protoc-gen-doc/flags.go
@@ -83,8 +83,8 @@ func (f *Flags) PrintVersion() {
 // ParseFlags parses the supplied options are returns a `Flags` object to the caller.
 //
 // Parameters:
-//   * `w` - the `io.Writer` to use for printing messages (help, version, etc.)
-//   * `args` - the set of args the program was invoked with (typically `os.Args`)
+//   - `w` - the `io.Writer` to use for printing messages (help, version, etc.)
+//   - `args` - the set of args the program was invoked with (typically `os.Args`)
 func ParseFlags(w io.Writer, args []string) *Flags {
 	f := Flags{appName: args[0], writer: w}
 
diff --git a/cmd/protoc-gen-doc/main.go b/cmd/protoc-gen-doc/main.go
index 56e42ce4..fabfeebc 100644
--- a/cmd/protoc-gen-doc/main.go
+++ b/cmd/protoc-gen-doc/main.go
@@ -4,11 +4,11 @@
 //
 // Example: generate HTML documentation
 //
-//     protoc --doc_out=. --doc_opt=html,index.html protos/*.proto
+//	protoc --doc_out=. --doc_opt=html,index.html protos/*.proto
 //
 // Example: use a custom template
 //
-//     protoc --doc_out=. --doc_opt=custom.tmpl,docs.txt protos/*.proto
+//	protoc --doc_out=. --doc_opt=custom.tmpl,docs.txt protos/*.proto
 //
 // For more details, check out the README at https://github.com/pseudomuto/protoc-gen-doc
 package main
@@ -20,9 +20,10 @@ import (
 	"os"
 
 	gendoc "github.com/pseudomuto/protoc-gen-doc"
-	_ "github.com/pseudomuto/protoc-gen-doc/extensions/google_api_http" // imported for side effects
-	_ "github.com/pseudomuto/protoc-gen-doc/extensions/lyft_validate"   // imported for side effects
-	_ "github.com/pseudomuto/protoc-gen-doc/extensions/validator_field" // imported for side effects
+	_ "github.com/pseudomuto/protoc-gen-doc/extensions/google_api_field_behavior" // imported for side effects
+	_ "github.com/pseudomuto/protoc-gen-doc/extensions/google_api_http"           // imported for side effects
+	_ "github.com/pseudomuto/protoc-gen-doc/extensions/lyft_validate"             // imported for side effects
+	_ "github.com/pseudomuto/protoc-gen-doc/extensions/validator_field"           // imported for side effects
 )
 
 func main() {
diff --git a/doc.go b/doc.go
index e9bee30c..df9f6622 100644
--- a/doc.go
+++ b/doc.go
@@ -5,15 +5,15 @@
 //
 // Example: generate HTML documentation
 //
-//     protoc --doc_out=. --doc_opt=html,index.html protos/*.proto
+//	protoc --doc_out=. --doc_opt=html,index.html protos/*.proto
 //
 // Example: exclude patterns
 //
-//     protoc --doc_out=. --doc_opt=html,index.html:google/*,somedir/* protos/*.proto
+//	protoc --doc_out=. --doc_opt=html,index.html:google/*,somedir/* protos/*.proto
 //
 // Example: use a custom template
 //
-//     protoc --doc_out=. --doc_opt=custom.tmpl,docs.txt protos/*.proto
+//	protoc --doc_out=. --doc_opt=custom.tmpl,docs.txt protos/*.proto
 //
 // For more details, check out the README at https://github.com/pseudomuto/protoc-gen-doc
 package gendoc
diff --git a/extensions/google_api_field_behavior/google_api_field_behavior.go b/extensions/google_api_field_behavior/google_api_field_behavior.go
new file mode 100644
index 00000000..fa3423c3
--- /dev/null
+++ b/extensions/google_api_field_behavior/google_api_field_behavior.go
@@ -0,0 +1,30 @@
+package extensions
+
+import (
+	"github.com/pseudomuto/protoc-gen-doc/extensions"
+	"google.golang.org/genproto/googleapis/api/annotations"
+)
+
+type FieldBehaviorExtension struct {
+	Options []string `json:"options"`
+}
+
+func init() {
+	extensions.SetTransformer("google.api.field_behavior", func(payload interface{}) interface{} {
+		fb, ok := payload.([]annotations.FieldBehavior)
+		if !ok {
+			return nil
+		}
+
+		if len(fb) == 0 {
+			return nil
+		}
+
+		fbs := make([]string, len(fb))
+		for i, behavior := range fb {
+			fbs[i] = behavior.String()
+		}
+
+		return FieldBehaviorExtension{Options: fbs}
+	})
+}
diff --git a/extensions/google_api_field_behavior/google_api_field_behavior_test.go b/extensions/google_api_field_behavior/google_api_field_behavior_test.go
new file mode 100644
index 00000000..af346ec5
--- /dev/null
+++ b/extensions/google_api_field_behavior/google_api_field_behavior_test.go
@@ -0,0 +1,19 @@
+package extensions_test
+
+import (
+	"testing"
+
+	"github.com/pseudomuto/protoc-gen-doc/extensions"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/genproto/googleapis/api/annotations"
+)
+
+func TestTransform(t *testing.T) {
+	behavior := []annotations.FieldBehavior{annotations.FieldBehavior_REQUIRED}
+
+	transformed := extensions.Transform(map[string]interface{}{"google.api.field_behavior": behavior})
+	require.NotEmpty(t, transformed)
+
+	options := transformed["google.api.field_behavior"].(FieldBehaviorExtension).Options()
+	require.Equal(t, options, []string{annotations.FieldBehavior_REQUIRED.String()})
+}