diff --git a/adapter/docker/runtime.py b/adapter/docker/runtime.py
index 7806bff..d9a6ec9 100644
--- a/adapter/docker/runtime.py
+++ b/adapter/docker/runtime.py
@@ -94,11 +94,11 @@ class DockerSandboxRuntime(SandboxRuntime):
                         endpoint = self._endpoint_from_container(container)
                     except (DockerException, OSError, ValueError) as exc:
                         self._remove_created_container(container, str(chat_id), exc)
-                        raise SandboxStartError(str(chat_id)) from exc
+                        raise SandboxStartError(str(chat_id), str(exc)) from exc
                 except SandboxStartError:
                     raise
                 except (DockerException, OSError, ValueError) as exc:
-                    raise SandboxStartError(str(chat_id)) from exc
+                    raise SandboxStartError(str(chat_id), str(exc)) from exc
 
                 result = 'created'
                 span.set_attribute('container.id', container_id)
diff --git a/adapter/http/fastapi/routers/v1/router.py b/adapter/http/fastapi/routers/v1/router.py
index 1d0616b..cb71748 100644
--- a/adapter/http/fastapi/routers/v1/router.py
+++ b/adapter/http/fastapi/routers/v1/router.py
@@ -70,9 +70,10 @@ def create_sandbox(
             detail=str(exc),
         ) from exc
     except SandboxStartError as exc:
+        detail = f'{exc}: {exc.reason}' if exc.reason else str(exc)
         raise HTTPException(
             status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
-            detail=str(exc),
+            detail=detail,
         ) from exc
     except SandboxError as exc:
         raise HTTPException(
diff --git a/domain/error.py b/domain/error.py
index 2bd2cc5..ca3a143 100644
--- a/domain/error.py
+++ b/domain/error.py
@@ -23,9 +23,10 @@ class SandboxError(DomainError):
 
 
 class SandboxStartError(SandboxError):
-    def __init__(self, chat_id: str) -> None:
+    def __init__(self, chat_id: str, reason: str = '') -> None:
         super().__init__('sandbox_start_failed')
         self.chat_id = chat_id
+        self.reason = reason
 
 
 class SandboxAlreadyRunningError(SandboxError):