Add warning callout re: bool and store_true defaults

nbs/06_script.ipynb

@@ -92,6 +92,22 @@
     "You should provide a default (after the `=`) for any *optional* parameters. If you don't provide a default for a parameter, then it will be a *positional* parameter."
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "::: {.callout-warning}\n",
+    "## Boolean Arguments Default to False\n",
+    "Arguments of type `bool` or `store_true` default to `False` regardless of whether you provide a default or not. Use `bool_arg` as the type instead of `bool` if you want to set a default value of True. For example:\n",
+    "\n",
+    "```python\n",
+    "@call_parse\n",
+    "def main(msg:str=\"Hi\",     # The message\n",
+    "         upper:bool_arg=True): # Convert to uppercase?\n",
+    "```\n",
+    ":::"
+   ]
+  },
   {
    "cell_type": "markdown",
    "metadata": {},