feat: Add streamable-http transport MCP support (#1777)

* Add streamable-http transport

* Improve error message for tool invocation

* Add streamable MCPTool example, update examples

* Improve examples

* Add unit tests

* Update integrations/mcp/examples/mcp_client.py

Co-authored-by: Amna Mubashar <[email protected]>

* initialize vars outside try block

* Small fix

* Fix linting

---------

Co-authored-by: Amna Mubashar <[email protected]>

Author: vblagoje

integrations/mcp/examples/google_maps_agent.py

@@ -0,0 +1,69 @@
+# SPDX-FileCopyrightText: 2022-present deepset GmbH <[email protected]>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import argparse
+import logging
+
+from haystack_integrations.tools.mcp import MCPTool, SSEServerInfo, StreamableHttpServerInfo
+
+# Setup targeted logging - only show debug logs from our package
+logging.basicConfig(level=logging.WARNING)  # Set root logger to WARNING
+mcp_logger = logging.getLogger("haystack_integrations.tools.mcp")
+mcp_logger.setLevel(logging.DEBUG)
+# Ensure we have at least one handler to avoid messages going to root logger
+if not mcp_logger.handlers:
+    handler = logging.StreamHandler()
+    handler.setFormatter(logging.Formatter("%(levelname)s:%(name)s:%(message)s"))
+    mcp_logger.addHandler(handler)
+    mcp_logger.propagate = False  # Prevent propagation to root logger
+
+# Run this client after running the server mcp_server.py
+# It shows how easy it is to use the MCPTool with different transport options
+
+
+def main():
+    """Example of MCPTool usage with server connection."""
+
+    # Parse command line arguments
+    parser = argparse.ArgumentParser(description="Run an MCP client to connect to the server")
+    parser.add_argument(
+        "--transport",
+        type=str,
+        default="sse",
+        choices=["sse", "streamable-http"],
+        help="Transport mechanism for the MCP client (default: sse)",
+    )
+    args = parser.parse_args()
+
+    # Construct the appropriate URL based on transport type
+    if args.transport == "sse":
+        server_info = SSEServerInfo(url="http://localhost:8000/sse")
+    else:  # streamable-http
+        server_info = StreamableHttpServerInfo(url="http://localhost:8000/mcp")
+    tool = None
+    tool_subtract = None
+    try:
+        tool = MCPTool(name="add", server_info=server_info)
+        tool_subtract = MCPTool(name="subtract", server_info=server_info)
+
+        result = tool.invoke(a=7, b=3)
+        print(f"7 + 3 = {result}")
+
+        result = tool_subtract.invoke(a=5, b=3)
+        print(f"5 - 3 = {result}")
+
+        result = tool.invoke(a=10, b=20)
+        print(f"10 + 20 = {result}")
+
+    except Exception as e:
+        print(f"Error in client example: {e}")
+    finally:
+        if tool:
+            tool.close()
+        if tool_subtract:
+            tool_subtract.close()
+
+
+if __name__ == "__main__":
+    main()

integrations/mcp/examples/mcp_client.py

@@ -6,18 +6,20 @@
 
 # This example demonstrates using MCPToolset with SSE transport
 # and filtering tools by name
-# Run this client after running the server mcp_sse_server.py
+# Run this client after running the server mcp_server.py with sse transport
 # It shows how MCPToolset can selectively include only specific tools
 
 
 def main():
     """Example of using MCPToolset with filtered tools."""
 
+    full_toolset = None
+    filtered_toolset = None
     try:
         print("Creating toolset with all available tools:")
         # Create a toolset with all available tools
         full_toolset = MCPToolset(
-            server_info=SSEServerInfo(base_url="http://localhost:8000"),
+            server_info=SSEServerInfo(url="http://localhost:8000/sse"),
         )
 
         # Print all discovered tools
@@ -29,7 +31,7 @@ def main():
         # Create a toolset with only specific tools
         # In this example, we're only including the 'add' tool
         filtered_toolset = MCPToolset(
-            server_info=SSEServerInfo(base_url="http://localhost:8000"),
+            server_info=SSEServerInfo(url="http://localhost:8000/sse"),
             tool_names=["add"],  # Only include the 'add' tool
         )
 
@@ -48,6 +50,11 @@ def main():
 
     except Exception as e:
         print(f"Error in filtered toolset example: {e}")
+    finally:
+        if full_toolset:
+            full_toolset.close()
+        if filtered_toolset:
+            filtered_toolset.close()
 
 
 if __name__ == "__main__":

integrations/mcp/examples/mcp_filtered_tools.py

@@ -0,0 +1,42 @@
+# SPDX-FileCopyrightText: 2022-present deepset GmbH <[email protected]>
+#
+# SPDX-License-Identifier: Apache-2.0
+
+import argparse
+
+from mcp.server.fastmcp import FastMCP
+
+# run this server first before running the client mcp_filtered_tools.py or mcp_client.py
+# it shows how easy it is to create a MCP server in just a few lines of code
+# then we'll use the MCPTool to invoke the server
+
+
+mcp = FastMCP("MCP Calculator")
+
+
+@mcp.tool()
+def add(a: int, b: int) -> int:
+    """Add two numbers"""
+    return a + b
+
+
+@mcp.tool()
+def subtract(a: int, b: int) -> int:
+    """Subtract two numbers"""
+    return a - b
+
+
+if __name__ == "__main__":
+    # Parse command line arguments
+    parser = argparse.ArgumentParser(
+        description="Run an MCP server with different transport options (sse or streamable-http)"
+    )
+    parser.add_argument(
+        "--transport",
+        type=str,
+        default="sse",
+        choices=["sse", "streamable-http"],
+        help="Transport mechanism for the MCP server (default: sse)",
+    )
+    args = parser.parse_args()
+    mcp.run(transport=args.transport)

integrations/mcp/examples/mcp_server.py

@@ -5,7 +5,7 @@
 from haystack_integrations.tools.mcp import MCPToolset, SSEServerInfo
 
 # This example demonstrates using MCPToolset with SSE transport
-# Run this client after running the server mcp_sse_server.py
+# Run this client after running the server mcp_server.py with sse transport
 # It shows how MCPToolset automatically discovers and creates tools from the MCP server
 
 
@@ -26,11 +26,12 @@ def find_tool(toolset, tool_name):
 def main():
     """Example of using MCPToolset with SSE transport."""
 
+    sse_toolset = None
     try:
         # Create the toolset - this automatically discovers all available tools
         # from the MCP server and creates Tool instances for each one
         sse_toolset = MCPToolset(
-            server_info=SSEServerInfo(base_url="http://localhost:8000"),
+            server_info=SSEServerInfo(url="http://localhost:8000/sse"),
         )
 
         # Print discovered tools
@@ -62,6 +63,10 @@ def main():
     except Exception as e:
         print(f"Error in SSE toolset example: {e}")
 
+    finally:
+        if sse_toolset:
+            sse_toolset.close()
+
 
 if __name__ == "__main__":
     main()

integrations/mcp/examples/mcp_sse_client.py

@@ -20,6 +20,7 @@
 def main():
     """Example of using the MCPTool implementation with stdio transport."""
 
+    stdio_tool = None
     try:
 
         stdio_tool = MCPTool(
@@ -36,6 +37,9 @@ def main():
         print(f"Current time in Los Angeles: {result}")
     except Exception as e:
         print(f"Error in stdio example: {e}")
+    finally:
+        if stdio_tool:
+            stdio_tool.close()
 
 
 if __name__ == "__main__":