[MCP server issue] Cannot access MCP server with env

[Yuanqi-babe]

What happened?

Describe the bug
I installed a Stdio MCP server following the configuration:
"github.com/mendableai/firecrawl-mcp-server": {
"command": "npx",
"args": ["-y", "firecrawl-mcp"],
"env": {
"FIRECRAWL_API_KEY": "fc-294547563d9344ef8409bbb8e80f5307"
},
"disabled": false,
"autoApprove": []
}
}

However, when I ran it in AutoGEN 0.4, it throws an unexpected error when registering MCP tools:

        logger.info("Setting up fetch MCP server...")
        fetch_mcp_server = StdioServerParams(command="env", args=["FIRECRAWL_API_KEY=fc-294547563d9344ef8409bbb8e80f5307", "npx", "-y" ,"firecrawl-mcp"])
        fetch_tools = await mcp_server_tools(fetch_mcp_server)
        logger.info(f"Fetch tools loaded: {len(fetch_tools)} tools")

Printed on the console it shows the successful onboard of this tool but:

FireCrawl MCP Server running on stdio
/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/pydantic/_internal/_fields.py:192: UserWarning: Field name "schema" in "DynamicModel" shadows an attribute in parent "BaseModel"
  warnings.warn(
2025-03-20 09:15:17,824 - ERROR
An error occurred: Each oneOf variant must have a type const
Traceback (most recent call last):
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/test_mcp.py", line 99, in main
    fetch_tools = await mcp_server_tools(fetch_mcp_server)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/autogen_ext/tools/mcp/_factory.py", line 139, in mcp_server_tools
    return [StdioMcpToolAdapter(server_params=server_params, tool=tool) for tool in tools.tools]
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/autogen_ext/tools/mcp/_stdio.py", line 48, in __init__
    super().__init__(server_params=server_params, tool=tool)
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/autogen_ext/tools/mcp/_base.py", line 36, in __init__
    input_model = create_model(tool.inputSchema)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/json_schema_to_pydantic/__init__.py", line 42, in create_model
    return builder.create_pydantic_model(schema, root_schema)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/json_schema_to_pydantic/model_builder.py", line 62, in create_pydantic_model
    field_type = self._get_field_type(field_schema, root_schema)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/json_schema_to_pydantic/model_builder.py", line 92, in _get_field_type
    return self.combiner_handler.handle_one_of(field_schema, root_schema)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/json_schema_to_pydantic/handlers.py", line 135, in handle_one_of
    raise CombinerError("Each oneOf variant must have a type const")
json_schema_to_pydantic.exceptions.CombinerError: Each oneOf variant must have a type const
Traceback (most recent call last):
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/test_mcp.py", line 173, in <module>
    asyncio.run(main())
  File "/usr/lib64/python3.12/asyncio/runners.py", line 194, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.12/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.12/asyncio/base_events.py", line 687, in run_until_complete
    return future.result()
           ^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/test_mcp.py", line 99, in main
    fetch_tools = await mcp_server_tools(fetch_mcp_server)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/autogen_ext/tools/mcp/_factory.py", line 139, in mcp_server_tools
    return [StdioMcpToolAdapter(server_params=server_params, tool=tool) for tool in tools.tools]
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/autogen_ext/tools/mcp/_stdio.py", line 48, in __init__
    super().__init__(server_params=server_params, tool=tool)
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/autogen_ext/tools/mcp/_base.py", line 36, in __init__
    input_model = create_model(tool.inputSchema)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/json_schema_to_pydantic/__init__.py", line 42, in create_model
    return builder.create_pydantic_model(schema, root_schema)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/json_schema_to_pydantic/model_builder.py", line 62, in create_pydantic_model
    field_type = self._get_field_type(field_schema, root_schema)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/json_schema_to_pydantic/model_builder.py", line 92, in _get_field_type
    return self.combiner_handler.handle_one_of(field_schema, root_schema)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/json_schema_to_pydantic/handlers.py", line 135, in handle_one_of
    raise CombinerError("Each oneOf variant must have a type const")
json_schema_to_pydantic.exceptions.CombinerError: Each oneOf variant must have a type const

To Reproduce

Which packages was the bug in?

Python Extensions (autogen-ext)

AutoGen library version.

Python dev (main branch)

Other library version.

-mcp

Model used

No response

Model provider

None

Other model provider

No response

Python version

3.12

.NET version

None

Operating system

CentOS

[ekzhu]

Could you print out your tool schema without using AutoGen from an mcp client? Looks like the tool schema cannot be used to create a json schema using pydantic:

  File "/home/ec2-user/bedrock-access-gw/bedrock-access-gateway/test-script/venv/lib64/python3.12/site-packages/autogen_ext/tools/mcp/_base.py", line 36, in __init__
    input_model = create_model(tool.inputSchema)

[ayhamakeed2000]

I have the same issue, are there any updates?

[ekzhu]

This should have been fixed in the latest version which relaxed the types requirement form JSON schema.

Some MCP servers are not producing standard JSON schema for list items, causing issue. Suggest also check with the creator of the MCP server for producing proper JSON schema in the future.