Allow kwargs down in AsyncClient when instantiating sse or streamable_http clients.

Author: patrick.rump

src/mcp/client/sse.py

@@ -26,12 +26,16 @@ async def sse_client(
     headers: dict[str, Any] | None = None,
     timeout: float = 5,
     sse_read_timeout: float = 60 * 5,
+    **client_kwargs: Any,
 ):
     """
     Client transport for SSE.
 
     `sse_read_timeout` determines how long (in seconds) the client will wait for a new
     event before disconnecting. All other HTTP operations are controlled by `timeout`.
+
+    `**client_kwargs` : dict, optional - Additional http client configurations used to configure the AsyncClient.
+
     """
     read_stream: MemoryObjectReceiveStream[SessionMessage | Exception]
     read_stream_writer: MemoryObjectSendStream[SessionMessage | Exception]
@@ -45,7 +49,9 @@ async def sse_client(
     async with anyio.create_task_group() as tg:
         try:
             logger.info(f"Connecting to SSE endpoint: {remove_request_params(url)}")
-            async with create_mcp_http_client(headers=headers) as client:
+            async with create_mcp_http_client(
+                headers=headers, client_kwargs=client_kwargs
+            ) as client:
                 async with aconnect_sse(
                     client,
                     "GET",

src/mcp/client/streamable_http.py

@@ -427,6 +427,7 @@ async def streamablehttp_client(
     timeout: timedelta = timedelta(seconds=30),
     sse_read_timeout: timedelta = timedelta(seconds=60 * 5),
     terminate_on_close: bool = True,
+    **client_kwargs: Any,
 ) -> AsyncGenerator[
     tuple[
         MemoryObjectReceiveStream[SessionMessage | Exception],
@@ -441,6 +442,8 @@ async def streamablehttp_client(
     `sse_read_timeout` determines how long (in seconds) the client will wait for a new
     event before disconnecting. All other HTTP operations are controlled by `timeout`.
 
+    `**client_kwargs` : dict, optional - Additional http client configurations used to configure the AsyncClient.
+
     Yields:
         Tuple containing:
             - read_stream: Stream for reading messages from the server
@@ -465,6 +468,7 @@ async def streamablehttp_client(
                 timeout=httpx.Timeout(
                     transport.timeout.seconds, read=transport.sse_read_timeout.seconds
                 ),
+                client_kwargs=client_kwargs,
             ) as client:
                 # Define callbacks that need access to tg
                 def start_get_stream() -> None:

src/mcp/shared/_httpx_utils.py

@@ -10,6 +10,7 @@
 def create_mcp_http_client(
     headers: dict[str, str] | None = None,
     timeout: httpx.Timeout | None = None,
+    client_kwargs: dict[str, Any] | None = None,
 ) -> httpx.AsyncClient:
     """Create a standardized httpx AsyncClient with MCP defaults.
 
@@ -21,6 +22,7 @@ def create_mcp_http_client(
         headers: Optional headers to include with all requests.
         timeout: Request timeout as httpx.Timeout object.
             Defaults to 30 seconds if not specified.
+        client_kwargs : dict[str, Any], optional. Used to configure the AsyncClient.
 
     Returns:
         Configured httpx.AsyncClient instance with MCP defaults.
@@ -45,18 +47,18 @@ def create_mcp_http_client(
             response = await client.get("/long-request")
     """
     # Set MCP defaults
-    kwargs: dict[str, Any] = {
-        "follow_redirects": True,
-    }
+    if not client_kwargs:
+        client_kwargs = {}
+    client_kwargs["follow_redirects"] = True
 
     # Handle timeout
     if timeout is None:
-        kwargs["timeout"] = httpx.Timeout(30.0)
+        client_kwargs["timeout"] = httpx.Timeout(30.0)
     else:
-        kwargs["timeout"] = timeout
+        client_kwargs["timeout"] = timeout
 
     # Handle headers
     if headers is not None:
-        kwargs["headers"] = headers
+        client_kwargs["headers"] = headers
 
-    return httpx.AsyncClient(**kwargs)
+    return httpx.AsyncClient(**client_kwargs)

tests/shared/test_httpx_utils.py

@@ -22,3 +22,11 @@ def test_custom_parameters():
 
     assert client.headers["Authorization"] == "Bearer token"
     assert client.timeout.connect == 60.0
+
+
+def test_client_kwargs_parameters():
+    """Test if additional kwargs are set correctly."""
+    client_kwargs = {"max_redirects": 999}
+
+    client = create_mcp_http_client(client_kwargs=client_kwargs)
+    assert client.max_redirects == 999