Fix tool propagation bug in hierarchical crews (#3679)

src/crewai/task.py

@@ -336,12 +336,6 @@ def set_attributes_based_on_config(self) -> "Task":
                 setattr(self, key, value)
         return self
 
-    @model_validator(mode="after")
-    def check_tools(self):
-        """Check if the tools are set."""
-        if not self.tools and self.agent and self.agent.tools:
-            self.tools.extend(self.agent.tools)
-        return self
 
     @model_validator(mode="after")
     def check_output(self):

tests/test_crew.py

@@ -200,7 +200,7 @@ def test_async_task_cannot_include_sequential_async_tasks_in_context(
     # This should raise an error because task2 is async and has task1 in its context without a sync task in between
     with pytest.raises(
         ValueError,
-        match="Task 'Task 2' is asynchronous and cannot include other sequential asynchronous tasks in its context.",
+        match=r"Task 'Task 2' is asynchronous and cannot include other sequential asynchronous tasks in its context.",
     ):
         Crew(tasks=[task1, task2, task3, task4, task5], agents=[researcher, writer])
 
@@ -238,7 +238,7 @@ def test_context_no_future_tasks(researcher, writer):
     # This should raise an error because task1 has a context dependency on a future task (task4)
     with pytest.raises(
         ValueError,
-        match="Task 'Task 1' has a context dependency on a future task 'Task 4', which is not allowed.",
+        match=r"Task 'Task 1' has a context dependency on a future task 'Task 4', which is not allowed.",
     ):
         Crew(tasks=[task1, task2, task3, task4], agents=[researcher, writer])
 
@@ -3339,7 +3339,7 @@ def test_replay_with_invalid_task_id():
     ):
         with pytest.raises(
             ValueError,
-            match="Task with id bf5b09c9-69bd-4eb8-be12-f9e5bae31c2d not found in the crew's tasks.",
+            match=r"Task with id bf5b09c9-69bd-4eb8-be12-f9e5bae31c2d not found in the crew's tasks.",
         ):
             crew.replay("bf5b09c9-69bd-4eb8-be12-f9e5bae31c2d")
 
@@ -3814,6 +3814,46 @@ def test_fetch_inputs():
     )
 
 
+def test_hierarchical_crew_does_not_propagate_agent_tools_to_manager():
+    """
+    Test that in hierarchical crews, manager agent doesn't inherit task agents' tools.
+    This verifies that the check_tools validator doesn't pollute task.tools at creation time.
+    Fixes issue #3679: https://github.com/crewAIInc/crewAI/issues/3679
+    """
+    from crewai.tools import tool
+
+    @tool
+    def agent_specific_tool() -> str:
+        """A tool that should only be available to the specific agent."""
+        return "agent specific result"
+
+    agent_with_tools = Agent(
+        role="Specialist",
+        goal="Do specialized work with custom tools",
+        backstory="You are a specialist with specific tools",
+        tools=[agent_specific_tool],
+        allow_delegation=False,
+    )
+
+    # Create a task with an agent that has tools, but don't assign tools to the task
+    task = Task(
+        description="Perform a specialized task",
+        expected_output="Task result",
+        agent=agent_with_tools,
+    )
+
+    Crew(
+        agents=[agent_with_tools],
+        tasks=[task],
+        process=Process.hierarchical,
+        manager_llm="gpt-4o",
+    )
+
+    # Verify that task.tools is empty (not populated with agent's tools)
+    assert task.tools == []
+    assert len(task.tools) == 0
+
+
 def test_task_tools_preserve_code_execution_tools():
     """
     Test that task tools don't override code execution tools when allow_code_execution=True

tests/test_task.py

@@ -20,11 +20,13 @@
 
 
 def test_task_tool_reflect_agent_tools():
+    """Test that agent tools are available during task execution via crew fallback logic."""
     from crewai.tools import tool
 
     @tool
-    def fake_tool() -> None:
+    def fake_tool() -> str:
         "Fake tool"
+        return "result"
 
     researcher = Agent(
         role="Researcher",
@@ -40,7 +42,9 @@ def fake_tool() -> None:
         agent=researcher,
     )
 
-    assert task.tools == [fake_tool]
+    assert task.tools == []
+
+    assert researcher.tools == [fake_tool]
 
 
 def test_task_tool_takes_precedence_over_agent_tools():
@@ -1218,7 +1222,7 @@ def test_create_directory_false():
     assert not resolved_dir.exists()
 
     with pytest.raises(
-        RuntimeError, match="Directory .* does not exist and create_directory is False"
+        RuntimeError, match=r"Directory .* does not exist and create_directory is False"
     ):
         task._save_file("test content")