DynamoDB: FastMCP.__init__() got an unexpected keyword argument 'version'

[neelmitra]

Describe the bug

All my working code using dynamodb mcp has started failing with the below error. The MCP clients are failing to initialize for the following.

aws_ddb_client = MCPClient(
lambda: stdio_client(
StdioServerParameters(
command="uvx",
args=[
"awslabs.dynamodb-mcp-server@latest"
],
env={
"DDB-MCP-READONLY": "false",
"AWS_PROFILE": "default",
"AWS_REGION": "us-east-1",
"FASTMCP_LOG_LEVEL": "ERROR"
},
disabled=False,
autoApprove=[]
)
)
)

Expected Behavior

MCP client should initialize successfully.

Current Behavior

Traceback (most recent call last):
File "/Users/indranem/.cache/uv/archive-v0/nt_jaja3XGQnmjA1kssMi/bin/awslabs.dynamodb-mcp-server", line 6, in
from awslabs.dynamodb_mcp_server.server import main
File "/Users/indranem/.cache/uv/archive-v0/nt_jaja3XGQnmjA1kssMi/lib/python3.13/site-packages/awslabs/dynamodb_mcp_server/server.py", line 56, in
app = FastMCP(
name='dynamodb-server',
...<51 lines>...
version='0.1.3',
)
TypeError: FastMCP.init() got an unexpected keyword argument 'version'
client failed to initialize

• Exception Group Traceback (most recent call last):
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 107, in start
  | self._init_future.result(timeout=30)
  | ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^
  | File "/opt/homebrew/Cellar/python@3.13/3.13.5/Frameworks/Python.framework/Versions/3.13/lib/python3.13/concurrent/futures/_base.py", line 456, in result
  | return self.__get_result()
  | ~~~~~~~~~~~~~~~~~^^
  | File "/opt/homebrew/Cellar/python@3.13/3.13.5/Frameworks/Python.framework/Versions/3.13/lib/python3.13/concurrent/futures/_base.py", line 401, in __get_result
  | raise self._exception
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 223, in _async_background_thread
  | async with self.transport_callable() as (read_stream, write_stream, *):
  | ~~~~~~~~~~~~~~~~~~~~~~~~^^
  | File "/opt/homebrew/Cellar/python@3.13/3.13.5/Frameworks/Python.framework/Versions/3.13/lib/python3.13/contextlib.py", line 235, in aexit
  | await self.gen.athrow(value)
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/client/stdio/init.py", line 173, in stdio_client
  | anyio.create_task_group() as tg,
  | ~~~~~~~~~~~~~~~~~~~~~~~^^
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/anyio/_backends/_asyncio.py", line 772, in aexit
  | raise BaseExceptionGroup(
  | "unhandled errors in a TaskGroup", self._exceptions
  | ) from None
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
  | Exception Group Traceback (most recent call last):
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/client/stdio/init.py", line 179, in stdio_client
  | yield read_stream, write_stream
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 225, in _async_background_thread
  | async with ClientSession(read_stream, write_stream) as session:
  | ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/shared/session.py", line 218, in aexit
  | return await self._task_group.aexit(exc_type, exc_val, exc_tb)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/anyio/_backends/_asyncio.py", line 772, in aexit
  | raise BaseExceptionGroup(
  | "unhandled errors in a TaskGroup", self._exceptions
  | ) from None
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
  | Traceback (most recent call last):
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 227, in _async_background_thread
  | await session.initialize()
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/client/session.py", line 123, in initialize
  | result = await self.send_request(
  | ^^^^^^^^^^^^^^^^^^^^^^^^
  | ...<15 lines>...
  | )
  | ^
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/shared/session.py", line 286, in send_request
  | raise McpError(response_or_error.error)
  | mcp.shared.exceptions.McpError: Connection closed
  +------------------------------------
• Exception Group Traceback (most recent call last):
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 107, in start
  | self._init_future.result(timeout=30)
  | ~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^
  | File "/opt/homebrew/Cellar/python@3.13/3.13.5/Frameworks/Python.framework/Versions/3.13/lib/python3.13/concurrent/futures/_base.py", line 456, in result
  | return self.__get_result()
  | ~~~~~~~~~~~~~~~~~^^
  | File "/opt/homebrew/Cellar/python@3.13/3.13.5/Frameworks/Python.framework/Versions/3.13/lib/python3.13/concurrent/futures/_base.py", line 401, in __get_result
  | raise self._exception
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 223, in _async_background_thread
  | async with self.transport_callable() as (read_stream, write_stream, *):
  | ~~~~~~~~~~~~~~~~~~~~~~~~^^
  | File "/opt/homebrew/Cellar/python@3.13/3.13.5/Frameworks/Python.framework/Versions/3.13/lib/python3.13/contextlib.py", line 235, in aexit
  | await self.gen.athrow(value)
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/client/stdio/init.py", line 173, in stdio_client
  | anyio.create_task_group() as tg,
  | ~~~~~~~~~~~~~~~~~~~~~~~^^
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/anyio/_backends/_asyncio.py", line 772, in aexit
  | raise BaseExceptionGroup(
  | "unhandled errors in a TaskGroup", self._exceptions
  | ) from None
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
  | Exception Group Traceback (most recent call last):
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/client/stdio/init.py", line 179, in stdio_client
  | yield read_stream, write_stream
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 225, in _async_background_thread
  | async with ClientSession(read_stream, write_stream) as session:
  | ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/shared/session.py", line 218, in aexit
  | return await self._task_group.aexit(exc_type, exc_val, exc_tb)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/anyio/_backends/_asyncio.py", line 772, in aexit
  | raise BaseExceptionGroup(
  | "unhandled errors in a TaskGroup", self._exceptions
  | ) from None
  | ExceptionGroup: unhandled errors in a TaskGroup (1 sub-exception)
  +-+---------------- 1 ----------------
  | Traceback (most recent call last):
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 227, in _async_background_thread
  | await session.initialize()
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/client/session.py", line 123, in initialize
  | result = await self.send_request(
  | ^^^^^^^^^^^^^^^^^^^^^^^^
  | ...<15 lines>...
  | )
  | ^
  | File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/mcp/shared/session.py", line 286, in send_request
  | raise McpError(response_or_error.error)
  | mcp.shared.exceptions.McpError: Connection closed
  +------------------------------------

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/mcp_ddb_strands_client.py", line 83, in
with aws_ddb_client, aws_kb_client:
^^^^^^^^^^^^^^
File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 80, in enter
return self.start()
~~~~~~~~~~^^
File "/Users/indranem/codespace/mcp/clients/strands_client/smart-home-strands/.venv/lib/python3.13/site-packages/strands/tools/mcp/mcp_client.py", line 113, in start
raise MCPClientInitializationError("the client initialization failed") from e

Reproduction Steps

Tried to reproduce from 2 different applications, both of which were working before, same issue.

Possible Solution

No response

Additional Information/Context

No response

OS

macos 15.5

Server

dynamodb-mcp-server

Server Version

No response

Region experiencing the issue

us-east-1

Other information

No response

Service quota

• I have reviewed the service quotas for this construct

[amarhyd]

I am seeing a similar issue with aws cost explorer mcp server. Init fails. It was working fine untill a couple of days ago.
Wonder what changed.

[neelmitra]

There are backward compatibility issue for MCP being tracked here - modelcontextprotocol/python-sdk#1198 (comment)

[sethgeoghegan]

Seeing the same for the DynamoDB MCP server

[relivnd]

Experiencing a similar issue with the ECS MCP. Here, the FastMCP is failing to initialize because of the description keyword.

Traceback (most recent call last):
  File "/Users/asdf/.cache/uv/archive-v0/fM-nIq6nkiZfB0W5xjMll/bin/ecs-mcp-server", line 6, in <module>
    from awslabs.ecs_mcp_server.main import main
  File "/Users/asdf/.cache/uv/archive-v0/fM-nIq6nkiZfB0W5xjMll/lib/python3.13/site-packages/awslabs/ecs_mcp_server/main.py", line 72, in <module>
    mcp = FastMCP(
        name="AWS ECS MCP Server",
    ...<29 lines>...
    """,
    )
TypeError: FastMCP.__init__() got an unexpected keyword argument 'description'

[LeeroyHannigan]

This issue was fixed already, FastMCP introduced a breaking change and we removed version from our MCP's.

https://github.com/awslabs/mcp/pull/1015/files