Introduce a function to create a standard AsyncClient with options (#655)

src/mcp/client/sse.py

@@ -10,6 +10,7 @@ from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStre
 from httpx_sse import aconnect_sse
 
 import mcp.types as types
+from mcp.shared._httpx_utils import create_mcp_http_client
 from mcp.shared.message import SessionMessage
 
 logger = logging.getLogger(__name__)
@@ -44,7 +45,7 @@ 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 httpx.AsyncClient(headers=headers) as client:
+            async with create_mcp_http_client(headers=headers) as client:
                 async with aconnect_sse(
                     client,
                     "GET",

src/mcp/client/streamable_http.py

@@ -18,6 +18,7 @@ import httpx
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
 from httpx_sse import EventSource, ServerSentEvent, aconnect_sse
 
+from mcp.shared._httpx_utils import create_mcp_http_client
 from mcp.shared.message import ClientMessageMetadata, SessionMessage
 from mcp.types import (
     ErrorData,
@@ -446,12 +447,11 @@ async def streamablehttp_client(
         try:
             logger.info(f"Connecting to StreamableHTTP endpoint: {url}")
 
-            async with httpx.AsyncClient(
+            async with create_mcp_http_client(
                 headers=transport.request_headers,
                 timeout=httpx.Timeout(
                     transport.timeout.seconds, read=transport.sse_read_timeout.seconds
                 ),
-                follow_redirects=True,
             ) as client:
                 # Define callbacks that need access to tg
                 def start_get_stream() -> None:

src/mcp/shared/_httpx_utils.py

@@ -0,0 +1,62 @@
+"""Utilities for creating standardized httpx AsyncClient instances."""
+
+from typing import Any
+
+import httpx
+
+__all__ = ["create_mcp_http_client"]
+
+
+def create_mcp_http_client(
+    headers: dict[str, str] | None = None,
+    timeout: httpx.Timeout | None = None,
+) -> httpx.AsyncClient:
+    """Create a standardized httpx AsyncClient with MCP defaults.
+
+    This function provides common defaults used throughout the MCP codebase:
+    - follow_redirects=True (always enabled)
+    - Default timeout of 30 seconds if not specified
+
+    Args:
+        headers: Optional headers to include with all requests.
+        timeout: Request timeout as httpx.Timeout object.
+            Defaults to 30 seconds if not specified.
+
+    Returns:
+        Configured httpx.AsyncClient instance with MCP defaults.
+
+    Note:
+        The returned AsyncClient must be used as a context manager to ensure
+        proper cleanup of connections.
+
+    Examples:
+        # Basic usage with MCP defaults
+        async with create_mcp_http_client() as client:
+            response = await client.get("https://api.example.com")
+
+        # With custom headers
+        headers = {"Authorization": "Bearer token"}
+        async with create_mcp_http_client(headers) as client:
+            response = await client.get("/endpoint")
+
+        # With both custom headers and timeout
+        timeout = httpx.Timeout(60.0, read=300.0)
+        async with create_mcp_http_client(headers, timeout) as client:
+            response = await client.get("/long-request")
+    """
+    # Set MCP defaults
+    kwargs: dict[str, Any] = {
+        "follow_redirects": True,
+    }
+
+    # Handle timeout
+    if timeout is None:
+        kwargs["timeout"] = httpx.Timeout(30.0)
+    else:
+        kwargs["timeout"] = timeout
+
+    # Handle headers
+    if headers is not None:
+        kwargs["headers"] = headers
+
+    return httpx.AsyncClient(**kwargs)