diff --git a/README.md b/README.md
index 9472ba8..0bbf608 100644
--- a/README.md
+++ b/README.md
@@ -37,7 +37,7 @@ class EchoApplication(ChatCompletion):
         # Generate response with a single choice
         with response.create_single_choice() as choice:
             # Fill the content of the response with the last user's content
-            choice.append_content(last_user_message.content or "")
+            choice.append_content(last_user_message.text)
 
 
 # DIALApp extends FastAPI to provide a user-friendly interface for routing requests to your applications
diff --git a/aidial_sdk/chat_completion/request.py b/aidial_sdk/chat_completion/request.py
index fe77596..a3821a1 100644
--- a/aidial_sdk/chat_completion/request.py
+++ b/aidial_sdk/chat_completion/request.py
@@ -1,8 +1,11 @@
 from enum import Enum
 from typing import Any, Dict, List, Literal, Mapping, Optional, Union
 
+from typing_extensions import assert_never
+
 from aidial_sdk.chat_completion.enums import Status
 from aidial_sdk.deployment.from_request_mixin import FromRequestDeploymentMixin
+from aidial_sdk.exceptions import InvalidRequestError
 from aidial_sdk.pydantic_v1 import (
     ConstrainedFloat,
     ConstrainedInt,
@@ -85,6 +88,20 @@ class Message(ExtraForbidModel):
     tool_call_id: Optional[StrictStr] = None
     function_call: Optional[FunctionCall] = None
 
+    @property
+    def text(self) -> str:
+        def _error_message(actual: str) -> str:
+            return f"Unable to retrieve text content of the message: the actual content is {actual}."
+
+        if self.content is None:
+            raise InvalidRequestError(_error_message("null or missing"))
+        elif isinstance(self.content, str):
+            return self.content
+        elif isinstance(self.content, list):
+            raise InvalidRequestError(_error_message("a list of content parts"))
+        else:
+            assert_never(self.content)
+
 
 class Addon(ExtraForbidModel):
     name: Optional[StrictStr] = None
diff --git a/examples/echo/app.py b/examples/echo/app.py
index 8304e25..efd55d6 100644
--- a/examples/echo/app.py
+++ b/examples/echo/app.py
@@ -20,11 +20,7 @@ async def chat_completion(
         # Generate response with a single choice
         with response.create_single_choice() as choice:
             # Fill the content of the response with the last user's content
-            choice.append_content(
-                last_message.content
-                if isinstance(last_message.content, str)
-                else ""
-            )
+            choice.append_content(last_message.text)
 
             if last_message.custom_content is not None:
                 for attachment in last_message.custom_content.attachments or []:
diff --git a/examples/langchain_rag/app.py b/examples/langchain_rag/app.py
index ee2a979..75ce290 100644
--- a/examples/langchain_rag/app.py
+++ b/examples/langchain_rag/app.py
@@ -61,7 +61,7 @@ async def chat_completion(
 
         with response.create_single_choice() as choice:
             message = request.messages[-1]
-            user_query = message.content or ""
+            user_query = message.text
 
             file_url = get_last_attachment_url(request.messages)
             file_abs_url = urljoin(f"{DIAL_URL}/v1/", file_url)
diff --git a/examples/render_text/app/main.py b/examples/render_text/app/main.py
index 88afa89..f7349ee 100644
--- a/examples/render_text/app/main.py
+++ b/examples/render_text/app/main.py
@@ -23,13 +23,12 @@ async def chat_completion(self, request: Request, response: Response):
         # Create a single choice
         with response.create_single_choice() as choice:
             # Get the last message content
-            content = request.messages[-1].content
-            content_text = content if isinstance(content, str) else ""
+            content = request.messages[-1].text
 
             # The image may be returned either as base64 string or as URL
             # The content specifies the mode of return: 'base64' or 'url'
             try:
-                command, text = content_text.split(",", 1)
+                command, text = content.split(",", 1)
                 if command not in ["base64", "url"]:
                     raise DIALException(
                         message="The command must be either 'base64' or 'url'",
diff --git a/tests/applications/broken_immediately.py b/tests/applications/broken_immediately.py
index 46edea6..e6d8851 100644
--- a/tests/applications/broken_immediately.py
+++ b/tests/applications/broken_immediately.py
@@ -2,7 +2,6 @@
 
 from aidial_sdk import HTTPException as DIALException
 from aidial_sdk.chat_completion import ChatCompletion, Request, Response
-from tests.utils.request import get_message_text_content
 
 
 def raise_exception(exception_type: str):
@@ -28,4 +27,4 @@ class BrokenApplication(ChatCompletion):
     async def chat_completion(
         self, request: Request, response: Response
     ) -> None:
-        raise_exception(get_message_text_content(request.messages[0]))
+        raise_exception(request.messages[0].text)
diff --git a/tests/applications/broken_in_runtime.py b/tests/applications/broken_in_runtime.py
index 62422db..4e22ef6 100644
--- a/tests/applications/broken_in_runtime.py
+++ b/tests/applications/broken_in_runtime.py
@@ -1,6 +1,5 @@
 from aidial_sdk.chat_completion import ChatCompletion, Request, Response
 from tests.applications.broken_immediately import raise_exception
-from tests.utils.request import get_message_text_content
 
 
 class RuntimeBrokenApplication(ChatCompletion):
@@ -18,4 +17,4 @@ async def chat_completion(
             choice.append_content("Test content")
             await response.aflush()
 
-            raise_exception(get_message_text_content(request.messages[0]))
+            raise_exception(request.messages[0].text)
diff --git a/tests/applications/echo.py b/tests/applications/echo.py
index 390e47c..169eeb5 100644
--- a/tests/applications/echo.py
+++ b/tests/applications/echo.py
@@ -6,7 +6,6 @@
     TruncatePromptRequest,
     TruncatePromptResponse,
 )
-from tests.utils.request import get_message_text_content
 from tests.utils.tokenization import (
     default_truncate_prompt,
     make_batched_tokenize,
@@ -28,7 +27,7 @@ async def chat_completion(
         response.set_response_id("test_id")
         response.set_created(0)
 
-        content = get_message_text_content(request.messages[-1])
+        content = request.messages[-1].text
 
         with response.create_single_choice() as choice:
             choice.append_content(content)
diff --git a/tests/test_errors.py b/tests/test_errors.py
index a0caa94..37468cb 100644
--- a/tests/test_errors.py
+++ b/tests/test_errors.py
@@ -51,6 +51,28 @@
             }
         },
     ),
+    (
+        None,
+        400,
+        {
+            "error": {
+                "message": "Unable to retrieve text content of the message: the actual content is null or missing.",
+                "type": "invalid_request_error",
+                "code": "400",
+            }
+        },
+    ),
+    (
+        [{"type": "text", "text": "hello"}],
+        400,
+        {
+            "error": {
+                "message": "Unable to retrieve text content of the message: the actual content is a list of content parts.",
+                "type": "invalid_request_error",
+                "code": "400",
+            }
+        },
+    ),
 ]
 
 
@@ -72,10 +94,8 @@ def test_error(type, response_status_code, response_content):
         headers={"Api-Key": "TEST_API_KEY"},
     )
 
-    assert (
-        response.status_code == response_status_code
-        and response.json() == response_content
-    )
+    assert response.status_code == response_status_code
+    assert response.json() == response_content
 
 
 @pytest.mark.parametrize(
@@ -96,10 +116,8 @@ def test_streaming_error(type, response_status_code, response_content):
         headers={"Api-Key": "TEST_API_KEY"},
     )
 
-    assert (
-        response.status_code == response_status_code
-        and response.json() == response_content
-    )
+    assert response.status_code == response_status_code
+    assert response.json() == response_content
 
 
 @pytest.mark.parametrize(
@@ -184,4 +202,5 @@ def test_no_api_key():
         },
     )
 
-    assert response.status_code == 400 and response.json() == API_KEY_IS_MISSING
+    assert response.status_code == 400
+    assert response.json() == API_KEY_IS_MISSING
diff --git a/tests/utils/request.py b/tests/utils/request.py
deleted file mode 100644
index 514f38c..0000000
--- a/tests/utils/request.py
+++ /dev/null
@@ -1,18 +0,0 @@
-from typing import List
-
-from aidial_sdk.chat_completion.request import Message, MessageContentTextPart
-
-
-def get_message_text_content(message: Message) -> str:
-    texts: List[str] = []
-
-    content = message.content
-
-    if isinstance(content, str):
-        return content
-    elif isinstance(content, list):
-        for part in content:
-            if isinstance(part, MessageContentTextPart):
-                texts.append(part.text)
-
-    return "\n".join(texts)
diff --git a/tests/utils/tokenization.py b/tests/utils/tokenization.py
index 87bde2a..6fc7014 100644
--- a/tests/utils/tokenization.py
+++ b/tests/utils/tokenization.py
@@ -19,7 +19,6 @@
     TruncatePromptResult,
     TruncatePromptSuccess,
 )
-from tests.utils.request import get_message_text_content
 
 
 def word_count_string(string: str) -> int:
@@ -27,7 +26,7 @@ def word_count_string(string: str) -> int:
 
 
 def word_count_message(message: Message) -> int:
-    return word_count_string(get_message_text_content(message))
+    return word_count_string(message.text)
 
 
 def word_count_request(request: ChatCompletionRequest) -> int: