diff --git a/docs/source/user-guides.rst b/docs/source/user-guides.rst
index 0b2bfdb..29cdb19 100644
--- a/docs/source/user-guides.rst
+++ b/docs/source/user-guides.rst
@@ -45,6 +45,22 @@ You can build the expected EIP-712 typed data for each execute via :mod:`nado_pr
     >>> order = OrderParams(amount=to_x18(20000), priceX18=to_pow_10(1, 17), expiration=order_expiration, nonce=order_nonce, sender=sender, appendix=appendix)
     >>> order_typed_data = build_eip712_typed_data(NadoExecuteType.PLACE_ORDER, order.dict(), verifying_contract, chain_id)
 
+**Market Order Example:**
+
+
+``place_market_order`` is synchronous and returns an ``ExecuteResponse`` directly. Do not await the call. The ``sender`` field must be a ``SubaccountParams`` instance, not a plain wallet address string.
+
+.. code-block:: python
+
+    >>> from nado_protocol.engine_client.types import PlaceMarketOrderParams
+    >>> from nado_protocol.utils.execute import MarketOrderParams
+    >>> from nado_protocol.utils.subaccount import SubaccountParams
+    >>> # ``client`` is an initialized NadoClient instance.
+    >>> sender = SubaccountParams(subaccount_owner="0xYourWalletAddress", subaccount_name="default")
+    >>> market_order = MarketOrderParams(sender=sender, amount=1)
+    >>> params = PlaceMarketOrderParams(product_id=1, market_order=market_order)
+    >>> response = client.market.place_market_order(params)
+
 **Other Execute Types Example:**
 
 .. code-block:: python
diff --git a/nado_protocol/client/apis/market/execute.py b/nado_protocol/client/apis/market/execute.py
index f47d15d..a9de70f 100644
--- a/nado_protocol/client/apis/market/execute.py
+++ b/nado_protocol/client/apis/market/execute.py
@@ -82,6 +82,8 @@ def place_market_order(self, params: PlaceMarketOrderParams) -> ExecuteResponse:
         """
         Places a market order through the engine.
 
+        This method is synchronous. Do not use ``await`` with the return value.
+
         Args:
             params (PlaceMarketOrderParams): Parameters required to place a market order.
 
diff --git a/nado_protocol/utils/execute.py b/nado_protocol/utils/execute.py
index b2eb5d2..9c06c94 100644
--- a/nado_protocol/utils/execute.py
+++ b/nado_protocol/utils/execute.py
@@ -81,6 +81,10 @@ class MarketOrderParams(BaseParams):
     """
     Class for defining the parameters of a market order.
 
+    The ``sender`` field inherited from ``BaseParams`` must be a
+    ``SubaccountParams`` instance. A plain wallet address string is not valid
+    for this parameter.
+
     Attributes:
         amount (int): The amount of the asset to be bought or sold in the order. Positive for a `long` position and negative for a `short`.