feat: Streamable HTTP support (#643)

Co-authored-by: aagarwal25 <akshit_agarwal@intuit.com>

Author: Akshit97

examples/mcp/streamablehttp_example/README.md

@@ -0,0 +1,13 @@
+# MCP Streamable HTTP Example
+
+This example uses a local Streamable HTTP server in [server.py](server.py).
+
+Run the example via:
+
+```
+uv run python examples/mcp/streamablehttp_example/main.py
+```
+
+## Details
+
+The example uses the `MCPServerStreamableHttp` class from `agents.mcp`. The server runs in a sub-process at `https://localhost:8000/mcp`.

examples/mcp/streamablehttp_example/main.py

@@ -0,0 +1,83 @@
+import asyncio
+import os
+import shutil
+import subprocess
+import time
+from typing import Any
+
+from agents import Agent, Runner, gen_trace_id, trace
+from agents.mcp import MCPServer, MCPServerStreamableHttp
+from agents.model_settings import ModelSettings
+
+
+async def run(mcp_server: MCPServer):
+    agent = Agent(
+        name="Assistant",
+        instructions="Use the tools to answer the questions.",
+        mcp_servers=[mcp_server],
+        model_settings=ModelSettings(tool_choice="required"),
+    )
+
+    # Use the `add` tool to add two numbers
+    message = "Add these numbers: 7 and 22."
+    print(f"Running: {message}")
+    result = await Runner.run(starting_agent=agent, input=message)
+    print(result.final_output)
+
+    # Run the `get_weather` tool
+    message = "What's the weather in Tokyo?"
+    print(f"\n\nRunning: {message}")
+    result = await Runner.run(starting_agent=agent, input=message)
+    print(result.final_output)
+
+    # Run the `get_secret_word` tool
+    message = "What's the secret word?"
+    print(f"\n\nRunning: {message}")
+    result = await Runner.run(starting_agent=agent, input=message)
+    print(result.final_output)
+
+
+async def main():
+    async with MCPServerStreamableHttp(
+        name="Streamable HTTP Python Server",
+        params={
+            "url": "http://localhost:8000/mcp",
+        },
+    ) as server:
+        trace_id = gen_trace_id()
+        with trace(workflow_name="Streamable HTTP Example", trace_id=trace_id):
+            print(f"View trace: https://platform.openai.com/traces/trace?trace_id={trace_id}\n")
+            await run(server)
+
+
+if __name__ == "__main__":
+    # Let's make sure the user has uv installed
+    if not shutil.which("uv"):
+        raise RuntimeError(
+            "uv is not installed. Please install it: https://docs.astral.sh/uv/getting-started/installation/"
+        )
+
+    # We'll run the Streamable HTTP server in a subprocess. Usually this would be a remote server, but for this
+    # demo, we'll run it locally at http://localhost:8000/mcp
+    process: subprocess.Popen[Any] | None = None
+    try:
+        this_dir = os.path.dirname(os.path.abspath(__file__))
+        server_file = os.path.join(this_dir, "server.py")
+
+        print("Starting Streamable HTTP server at http://localhost:8000/mcp ...")
+
+        # Run `uv run server.py` to start the Streamable HTTP server
+        process = subprocess.Popen(["uv", "run", server_file])
+        # Give it 3 seconds to start
+        time.sleep(3)
+
+        print("Streamable HTTP server started. Running example...\n\n")
+    except Exception as e:
+        print(f"Error starting Streamable HTTP server: {e}")
+        exit(1)
+
+    try:
+        asyncio.run(main())
+    finally:
+        if process:
+            process.terminate()

examples/mcp/streamablehttp_example/server.py

@@ -0,0 +1,33 @@
+import random
+
+import requests
+from mcp.server.fastmcp import FastMCP
+
+# Create server
+mcp = FastMCP("Echo Server")
+
+
+@mcp.tool()
+def add(a: int, b: int) -> int:
+    """Add two numbers"""
+    print(f"[debug-server] add({a}, {b})")
+    return a + b
+
+
+@mcp.tool()
+def get_secret_word() -> str:
+    print("[debug-server] get_secret_word()")
+    return random.choice(["apple", "banana", "cherry"])
+
+
+@mcp.tool()
+def get_current_weather(city: str) -> str:
+    print(f"[debug-server] get_current_weather({city})")
+
+    endpoint = "https://wttr.in"
+    response = requests.get(f"{endpoint}/{city}")
+    return response.text
+
+
+if __name__ == "__main__":
+    mcp.run(transport="streamable-http")

pyproject.toml

@@ -13,7 +13,7 @@ dependencies = [
     "typing-extensions>=4.12.2, <5",
     "requests>=2.0, <3",
     "types-requests>=2.0, <3",
-    "mcp>=1.6.0, <2; python_version >= '3.10'",
+    "mcp>=1.8.0, <2; python_version >= '3.10'",
 ]
 classifiers = [
     "Typing :: Typed",

src/agents/mcp/__init__.py

@@ -5,6 +5,8 @@
         MCPServerSseParams,
         MCPServerStdio,
         MCPServerStdioParams,
+        MCPServerStreamableHttp,
+        MCPServerStreamableHttpParams,
     )
 except ImportError:
     pass
@@ -17,5 +19,7 @@
     "MCPServerSseParams",
     "MCPServerStdio",
     "MCPServerStdioParams",
+    "MCPServerStreamableHttp",
+    "MCPServerStreamableHttpParams",
     "MCPUtil",
 ]

src/agents/mcp/server.py

@@ -10,7 +10,9 @@
 from anyio.streams.memory import MemoryObjectReceiveStream, MemoryObjectSendStream
 from mcp import ClientSession, StdioServerParameters, Tool as MCPTool, stdio_client
 from mcp.client.sse import sse_client
-from mcp.types import CallToolResult, JSONRPCMessage
+from mcp.client.streamable_http import GetSessionIdCallback, streamablehttp_client
+from mcp.shared.message import SessionMessage
+from mcp.types import CallToolResult
 from typing_extensions import NotRequired, TypedDict
 
 from ..exceptions import UserError
@@ -83,8 +85,9 @@ def create_streams(
         self,
     ) -> AbstractAsyncContextManager[
         tuple[
-            MemoryObjectReceiveStream[JSONRPCMessage | Exception],
-            MemoryObjectSendStream[JSONRPCMessage],
+            MemoryObjectReceiveStream[SessionMessage | Exception],
+            MemoryObjectSendStream[SessionMessage],
+            GetSessionIdCallback | None
         ]
     ]:
         """Create the streams for the server."""
@@ -105,7 +108,11 @@ async def connect(self):
         """Connect to the server."""
         try:
             transport = await self.exit_stack.enter_async_context(self.create_streams())
-            read, write = transport
+            # streamablehttp_client returns (read, write, get_session_id)
+            # sse_client returns (read, write)
+
+            read, write, *_ = transport
+
             session = await self.exit_stack.enter_async_context(
                 ClientSession(
                     read,
@@ -232,8 +239,9 @@ def create_streams(
         self,
     ) -> AbstractAsyncContextManager[
         tuple[
-            MemoryObjectReceiveStream[JSONRPCMessage | Exception],
-            MemoryObjectSendStream[JSONRPCMessage],
+            MemoryObjectReceiveStream[SessionMessage | Exception],
+            MemoryObjectSendStream[SessionMessage],
+            GetSessionIdCallback | None
         ]
     ]:
         """Create the streams for the server."""
@@ -302,8 +310,9 @@ def create_streams(
         self,
     ) -> AbstractAsyncContextManager[
         tuple[
-            MemoryObjectReceiveStream[JSONRPCMessage | Exception],
-            MemoryObjectSendStream[JSONRPCMessage],
+            MemoryObjectReceiveStream[SessionMessage | Exception],
+            MemoryObjectSendStream[SessionMessage],
+            GetSessionIdCallback | None
         ]
     ]:
         """Create the streams for the server."""
@@ -318,3 +327,84 @@ def create_streams(
     def name(self) -> str:
         """A readable name for the server."""
         return self._name
+
+
+class MCPServerStreamableHttpParams(TypedDict):
+    """Mirrors the params in`mcp.client.streamable_http.streamablehttp_client`."""
+
+    url: str
+    """The URL of the server."""
+
+    headers: NotRequired[dict[str, str]]
+    """The headers to send to the server."""
+
+    timeout: NotRequired[timedelta]
+    """The timeout for the HTTP request. Defaults to 5 seconds."""
+
+    sse_read_timeout: NotRequired[timedelta]
+    """The timeout for the SSE connection, in seconds. Defaults to 5 minutes."""
+
+    terminate_on_close: NotRequired[bool]
+    """Terminate on close"""
+
+
+class MCPServerStreamableHttp(_MCPServerWithClientSession):
+    """MCP server implementation that uses the Streamable HTTP transport. See the [spec]
+    (https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#streamable-http)
+    for details.
+    """
+
+    def __init__(
+        self,
+        params: MCPServerStreamableHttpParams,
+        cache_tools_list: bool = False,
+        name: str | None = None,
+        client_session_timeout_seconds: float | None = 5,
+    ):
+        """Create a new MCP server based on the Streamable HTTP transport.
+
+        Args:
+            params: The params that configure the server. This includes the URL of the server,
+                the headers to send to the server, the timeout for the HTTP request, and the
+                timeout for the Streamable HTTP connection and whether we need to
+                terminate on close.
+
+            cache_tools_list: Whether to cache the tools list. If `True`, the tools list will be
+                cached and only fetched from the server once. If `False`, the tools list will be
+                fetched from the server on each call to `list_tools()`. The cache can be
+                invalidated by calling `invalidate_tools_cache()`. You should set this to `True`
+                if you know the server will not change its tools list, because it can drastically
+                improve latency (by avoiding a round-trip to the server every time).
+
+            name: A readable name for the server. If not provided, we'll create one from the
+                URL.
+
+            client_session_timeout_seconds: the read timeout passed to the MCP ClientSession.
+        """
+        super().__init__(cache_tools_list, client_session_timeout_seconds)
+
+        self.params = params
+        self._name = name or f"streamable_http: {self.params['url']}"
+
+    def create_streams(
+        self,
+    ) -> AbstractAsyncContextManager[
+        tuple[
+            MemoryObjectReceiveStream[SessionMessage | Exception],
+            MemoryObjectSendStream[SessionMessage],
+            GetSessionIdCallback | None
+        ]
+    ]:
+        """Create the streams for the server."""
+        return streamablehttp_client(
+            url=self.params["url"],
+            headers=self.params.get("headers", None),
+            timeout=self.params.get("timeout", timedelta(seconds=30)),
+            sse_read_timeout=self.params.get("sse_read_timeout", timedelta(seconds=60 * 5)),
+            terminate_on_close=self.params.get("terminate_on_close", True)
+        )
+
+    @property
+    def name(self) -> str:
+        """A readable name for the server."""
+        return self._name