diff --git a/mcp_servers/rag_server.py b/mcp_servers/rag_server.py
index d70aa1c..1dfd464 100644
--- a/mcp_servers/rag_server.py
+++ b/mcp_servers/rag_server.py
@@ -101,7 +101,8 @@ async def call_tool(name: str, arguments: dict) -> list[TextContent]:
             return [TextContent(type="text", text=f"Error: {e}")]
 
     elif action == "add_directory":
-        directory = arguments.get("directory", "").strip()
+        _dir = arguments.get("directory")
+        directory = _dir.strip() if isinstance(_dir, str) else ""
         if not directory:
             return [TextContent(type="text", text="Error: add_directory needs a directory path")]
         directory = os.path.expanduser(directory)
@@ -126,7 +127,8 @@ async def call_tool(name: str, arguments: dict) -> list[TextContent]:
             return [TextContent(type="text", text=f"Error: Failed to index directory: {e}")]
 
     elif action == "remove_directory":
-        directory = arguments.get("directory", "").strip()
+        _dir = arguments.get("directory")
+        directory = _dir.strip() if isinstance(_dir, str) else ""
         if not directory:
             return [TextContent(type="text", text="Error: remove_directory needs a directory path")]
         # Expand ~ to match add_directory, which indexes the expanded path.
diff --git a/tests/test_rag_server_directory_nonstring.py b/tests/test_rag_server_directory_nonstring.py
new file mode 100644
index 0000000..4311cf5
--- /dev/null
+++ b/tests/test_rag_server_directory_nonstring.py
@@ -0,0 +1,28 @@
+"""Regression: rag_server add/remove_directory must not crash on a non-string path.
+
+`directory = arguments.get("directory", "").strip()` runs before the surrounding
+try, so a non-string `directory` in the tool args (e.g. a number) raised
+AttributeError out of call_tool. Coerce non-strings to "".
+"""
+import asyncio
+
+import pytest
+
+pytest.importorskip("mcp")
+
+import mcp_servers.rag_server as rs
+
+
+def _call(monkeypatch, action, directory):
+    monkeypatch.setattr(rs, "_ensure_init", lambda: None)
+    return asyncio.run(rs.call_tool("manage_rag", {"action": action, "directory": directory}))
+
+
+def test_add_directory_non_string_does_not_crash(monkeypatch):
+    out = _call(monkeypatch, "add_directory", 123)
+    assert "needs a directory path" in out[0].text
+
+
+def test_remove_directory_non_string_does_not_crash(monkeypatch):
+    out = _call(monkeypatch, "remove_directory", ["x"])
+    assert "needs a directory path" in out[0].text