Bug: Filter out `None` values in` _run` method of `crewai_adapter.py`

[freddo1503]

Description

When running a CrewAI agent that uses the list_pull_requests tool from the GitHub MCP server, the following error is encountered:

parameter head is not of type string, is <nil>

Error Response from the MCP server

{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "content": [
      {
        "type": "text",
        "text": "parameter head is not of type string, is \u003cnil\u003e"
      }
    ],
    "isError": true
  }
}

Steps to Reproduce

1. Run the agent using the code below.

import os
from mcp import StdioServerParameters
from crewai import Agent, Task, Crew
from crewai_tools import MCPServerAdapter

GITHUB_TOKEN = os.getenv("GITHUB_PERSONAL_ACCESS_TOKEN")
GITHUB_USER = os.getenv("GITHUB_USERNAME")
GITHUB_REPO = os.getenv("GITHUB_REPOSITORY")

if not GITHUB_TOKEN:
    raise EnvironmentError("Please set the GITHUB_PERSONAL_ACCESS_TOKEN environment variable.")

server_params = StdioServerParameters(
    command="docker",
    args=[
        "run", "-i", "--rm",
        "-e", f"GITHUB_PERSONAL_ACCESS_TOKEN={GITHUB_TOKEN}",
        "ghcr.io/github/github-mcp-server"
    ]
)

with MCPServerAdapter(server_params) as tools:
    agent = Agent(
        role="GitHub Pull Request Analyst",
        goal="Identify and summarize open pull requests",
        backstory="You specialize in GitHub workflows and analyze open PRs.",
        tools=tools,
        verbose=True
    )

    task = Task(
        description=(
            f"Retrieve and summarize open PRs for '{GITHUB_USER}/{GITHUB_REPO}' "
            f"using the 'list_pull_requests' tool. Only pass non-empty fields as strings."
        ),
        expected_output=(
            f"- PR number\n- Title\n- Status\n- Author\n- Optional summary"
        ),
        agent=agent
    )

    crew = Crew(agents=[agent], tasks=[task])
    crew.kickoff()

Proposed Fix (in crewai_adapter.py)

Current:

def _run(self, *args: Any, **kwargs: Any) -> Any:
    print("args", args)
    print("kwargs", kwargs)
    return func(kwargs).content[0].text

Suggested:

def _run(self, *args: Any, **kwargs: Any) -> Any:
    print("args", args)
    print("kwargs", kwargs)
    processed_kwargs = {k: v for k, v in kwargs.items() if v is not None}
    return func(processed_kwargs).content[0].text

[grll]

Hi @freddo1503 thanks for raising the issue I will have a look as soon as possible!

[grll]

Hey @freddo1503 I am having a look at it right now.

Look like the issue is because in the go implementation of the github mcp server you can't pass a None parameter to optional parameters as it is usually the case in python. It needs to be of the right expected type or not provided at all.

The issue I have with the fix you mentioned here is that it would basically make it impossible to pass a parameter with a None value.

I will try to find a solution that still allows to pass None value parameter if needed, it could be required by some other mcp to pass None values for certain behaviors...

[grll]

PR #49 fixes the issue.
I have tested it with the following:

print("Testing CrewAI adapter with GitHub MCP server...")
print("This test verifies that None values don't cause 'parameter X is not of type string, is <nil>' errors")
print("-" * 80)

server_params = StdioServerParameters(
    command="docker",
    args=[
        "run", "-i", "--rm",
        "-e", f"GITHUB_PERSONAL_ACCESS_TOKEN={GITHUB_TOKEN}",
        "ghcr.io/github/github-mcp-server"
    ]
)

try:
    print("\nConnecting to GitHub MCP server...")
    with MCPAdapt(server_params, CrewAIAdapter()) as tools:
        print(f"✅ Connected successfully! Found {len(tools)} tools")
        
        # Find the list_pull_requests tool
        list_pr_tool = None
        for tool in tools:
            if tool.name == "list_pull_requests":
                list_pr_tool = tool
                break
        
        if list_pr_tool:
            print(f"\n✅ Found 'list_pull_requests' tool")
            
            # This is the key test - pass None values for optional parameters
            # Before the fix, this would cause: "parameter head is not of type string, is <nil>"
            print("\nTesting with None values for optional parameters...")
            try:
                # Pass required parameters and None for optional ones
                # The schema for list_pull_requests has owner and repo as required,
                # and head, base, state as optional string parameters
                result = list_pr_tool.run(
                    owner="grll",
                    repo="mcpadapt",
                    head=None,  # This would cause the error before our fix
                    base=None,  # This would cause the error before our fix
                    state=None  # This would cause the error before our fix
                )
                
                # If we get here without error, the fix is working
                print("\n✅ SUCCESS! None values were handled correctly")
                print(f"Result type: {type(result)}")
                print(f"Result preview: {str(result)[:200]}...")
                
                # Check that we didn't get the specific error
                if "is not of type string, is <nil>" in str(result):
                    print("\n❌ FAILURE: Got the 'is <nil>' error in the result")
                else:
                    print("\n✅ No 'is <nil>' error found - fix is working!")
                    
            except Exception as e:
                error_msg = str(e)
                if "is not of type string, is <nil>" in error_msg:
                    print(f"\n❌ FAILURE: Got the None value error: {error_msg}")
                else:
                    print(f"\n⚠️  Got a different error: {error_msg}")
                    if "401" in error_msg or "Unauthorized" in error_msg:
                        print("   (This is likely an auth error with dummy token, not the None value issue)")
                        print("   ✅ The fix is still working - no 'is <nil>' error!")
        else:
            print("\n❌ Could not find 'list_pull_requests' tool in available tools:")
            for i, tool in enumerate(tools[:5]):  # Show first 5 tools
                print(f"   {i+1}. {tool.name}")
            if len(tools) > 5:
                print(f"   ... and {len(tools) - 5} more")
                
except Exception as e:
    error_msg = str(e)
    print(f"\n❌ Error connecting to server: {error_msg}")
    if "docker" in error_msg.lower():
        print("   Make sure Docker is running and the GitHub MCP server image is available")
    elif "is not of type string, is <nil>" in error_msg:
        print("   ❌ This is the bug we're trying to fix!")

print("\n" + "-" * 80)
print("Test complete.")