diff --git a/lib/models/step_request_body.dart b/lib/models/step_request_body.dart
new file mode 100644
index 00000000..6f8fb7cb
--- /dev/null
+++ b/lib/models/step_request_body.dart
@@ -0,0 +1,10 @@
+class StepRequestBody {
+  final String input;
+  final Map<String, dynamic>? additionalInput;
+
+  StepRequestBody({required this.input, this.additionalInput});
+
+  Map<String, dynamic> toJson() {
+    return {'input': input, 'additional_input': additionalInput};
+  }
+}
diff --git a/test/step_request_body_test.dart b/test/step_request_body_test.dart
new file mode 100644
index 00000000..d15a95f6
--- /dev/null
+++ b/test/step_request_body_test.dart
@@ -0,0 +1,26 @@
+import 'package:auto_gpt_flutter_client/models/step_request_body.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('StepRequestBody', () {
+    test('should create StepRequestBody with correct values', () {
+      final stepRequestBody = StepRequestBody(
+          input: 'Execute something', additionalInput: {'key': 'value'});
+
+      expect(stepRequestBody.input, 'Execute something');
+      expect(stepRequestBody.additionalInput, {'key': 'value'});
+    });
+
+    test('should convert StepRequestBody to correct JSON', () {
+      final stepRequestBody = StepRequestBody(
+          input: 'Execute something', additionalInput: {'key': 'value'});
+
+      final json = stepRequestBody.toJson();
+
+      expect(json, {
+        'input': 'Execute something',
+        'additional_input': {'key': 'value'}
+      });
+    });
+  });
+}