[BUG]When I use mcps but tools is None, it will not load mcp tools

[kid0317]

Description

when I use mcp like this

sandbox_agent = Agent(
role="…",
goal="…",
backstory="…",
mcps=[
        MCPServerHTTP(
            url="http://localhost:8022/mcp",  
        )
    ],
)

mcp will not load. I check the source code at crewai/agent/core.py ,

if mcps and self.tools is not None:
        self.tools.extend(mcps)

Steps to Reproduce

use mcps but tools is None

Expected behavior

can just use mcps

Screenshots/Code snippets

above

Operating System

macOS Ventura

Python Version

3.10

crewAI Version

1.7.2

crewAI Tools Version

1.7.2

Virtual Environment

Venv

Evidence

if mcps and self.tools is not None:
self.tools.extend(mcps)

Possible Solution

when tools is None, let it []

Additional context

no more

[xXMrNidaXx]

Good catch! This is a logic bug in the condition.

The Issue

if mcps and self.tools is not None:
    self.tools.extend(mcps)

When you don't pass tools, it defaults to None. The condition self.tools is not None is False, so the MCP tools never get added — even though you explicitly passed them.

Workaround (Until Fixed)

Just pass an empty list for tools:

sandbox_agent = Agent(
    role="…",
    goal="…",
    backstory="…",
    tools=[],  # ← This makes self.tools not None
    mcps=[
        MCPServerHTTP(url="http://localhost:8022/mcp")
    ],
)

The Fix

Your suggested fix is correct. The code should be:

if mcps:
    if self.tools is None:
        self.tools = []
    self.tools.extend(mcps)

This ensures MCP tools are added regardless of whether tools was explicitly provided. Might be worth opening a PR — it's a one-liner fix.

---

We've hit similar MCP integration issues at RevolutionAI — happy to help test a fix if one gets merged.

[xXMrNidaXx]

Good catch! The conditional logic is indeed the issue.

Workaround until this is fixed:

sandbox_agent = Agent(
    role="...",
    goal="...",
    backstory="...",
    tools=[],  # Pass empty list instead of None
    mcps=[
        MCPServerHTTP(
            url="http://localhost:8022/mcp",  
        )
    ],
)

By passing tools=[] instead of leaving it as None, the MCP tools will be properly loaded and extended onto the tools list.

The fix in source would be:

# Instead of:
if mcps and self.tools is not None:
    self.tools.extend(mcps)

# Should be:
if mcps:
    if self.tools is None:
        self.tools = []
    self.tools.extend(mcps)

This ensures MCPs work standalone without requiring pre-existing tools.