Adding support to force a tool return to be the final answer. (#867)

* Adding support to force a tool return to be the final answer.
This will at the end of the execution return the tool output.
It will return the output of the latest tool with the flag

* Update src/crewai/agent.py

Co-authored-by: Gui Vieira <guilherme_vieira@me.com>

* Update tests/agent_test.py

Co-authored-by: Gui Vieira <guilherme_vieira@me.com>

---------

Co-authored-by: Gui Vieira <guilherme_vieira@me.com>

tests/agent_test.py

@@ -723,6 +723,75 @@ def test_agent_count_formatting_error():
         mock_count_errors.assert_called_once()
 
 
+@pytest.mark.vcr(filter_headers=["authorization"])
+def test_tool_result_as_answer_is_the_final_answer_for_the_agent():
+    from crewai_tools import BaseTool
+
+    class MyCustomTool(BaseTool):
+        name: str = "Get Greetings"
+        description: str = "Get a random greeting back"
+
+        def _run(self) -> str:
+            return "Howdy!"
+
+    agent1 = Agent(
+        role="Data Scientist",
+        goal="Product amazing resports on AI",
+        backstory="You work with data and AI",
+        tools=[MyCustomTool(result_as_answer=True)],
+    )
+
+    essay = Task(
+        description="Write and then review an small paragraph on AI until it's AMAZING. But first use the `Get Greetings` tool to get a greeting.",
+        expected_output="The final paragraph with the full review on AI and no greeting.",
+        agent=agent1,
+    )
+    tasks = [essay]
+    crew = Crew(agents=[agent1], tasks=tasks)
+
+    result = crew.kickoff()
+    assert result == "Howdy!"
+
+
+pytest.mark.vcr(filter_headers=["authorization"])
+
+
+def test_tool_usage_information_is_appended_to_agent():
+    from crewai_tools import BaseTool
+
+    class MyCustomTool(BaseTool):
+        name: str = "Decide Greetings"
+        description: str = "Decide what is the appropriate greeting to use"
+
+        def _run(self) -> str:
+            return "Howdy!"
+
+    agent1 = Agent(
+        role="Friendly Neighbor",
+        goal="Make everyone feel welcome",
+        backstory="You are the friendly neighbor",
+        tools=[MyCustomTool(result_as_answer=True)],
+    )
+
+    greeting = Task(
+        description="Say an appropriate greeting.",
+        expected_output="The greeting.",
+        agent=agent1,
+    )
+    tasks = [greeting]
+    crew = Crew(agents=[agent1], tasks=tasks)
+
+    crew.kickoff()
+    assert agent1.tools_results == [
+        {
+            "result": "Howdy!",
+            "tool_name": "Decide Greetings",
+            "tool_args": {},
+            "result_as_answer": True,
+        }
+    ]
+
+
 def test_agent_llm_uses_token_calc_handler_with_llm_has_model_name():
     agent1 = Agent(
         role="test role",