diff --git a/src/tscut/exceptions.py b/src/tscut/exceptions.py
new file mode 100644
index 0000000..0aa19a0
--- /dev/null
+++ b/src/tscut/exceptions.py
@@ -0,0 +1,23 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright (C) 2026 Frédéric Tronel
+
+
+from typing import IO
+
+from typeguard import typechecked
+
+class TSCutError(Exception):
+    """Base exception for tscut."""
+
+
+class MissingToolError(TSCutError):
+    """Raised when a required external tool is unavailable."""
+
+
+class ExternalToolError(TSCutError):
+    """Raised when an external tool fails."""
+
+
+class InvalidMediaError(TSCutError):
+    """Raised when input media cannot be processed."""
diff --git a/src/tscut/tools/discovery.py b/src/tscut/tools/discovery.py
index b56a721..671f0ee 100644
--- a/src/tscut/tools/discovery.py
+++ b/src/tscut/tools/discovery.py
@@ -8,10 +8,10 @@ from shutil import which
 
 from typeguard import typechecked
 
+from tscut.exceptions import MissingToolError
+
 logger = logging.getLogger(__name__)
 
-class MissingToolError(Exception):
-    pass
 
 @typechecked
 def check_required_tools() -> tuple[bool,dict[str,str]]: