Brandon/improve llm structured output (#2029)

* code and tests work

* update docs

---------

Co-authored-by: Lorenze Jay <63378463+lorenzejay@users.noreply.github.com>

tests/llm_test.py

@@ -3,6 +3,7 @@ from time import sleep
 from unittest.mock import MagicMock, patch
 
 import pytest
+from pydantic import BaseModel
 
 from crewai.agents.agent_builder.utilities.base_token_process import TokenProcess
 from crewai.llm import LLM
@@ -205,6 +206,52 @@ def test_llm_passes_additional_params():
         assert result == "Test response"
 
 
+def test_get_custom_llm_provider_openrouter():
+    llm = LLM(model="openrouter/deepseek/deepseek-chat")
+    assert llm._get_custom_llm_provider() == "openrouter"
+
+
+def test_get_custom_llm_provider_gemini():
+    llm = LLM(model="gemini/gemini-1.5-pro")
+    assert llm._get_custom_llm_provider() == "gemini"
+
+
+def test_get_custom_llm_provider_openai():
+    llm = LLM(model="gpt-4")
+    assert llm._get_custom_llm_provider() == "openai"
+
+
+def test_validate_call_params_supported():
+    class DummyResponse(BaseModel):
+        a: int
+
+    # Patch supports_response_schema to simulate a supported model.
+    with patch("crewai.llm.supports_response_schema", return_value=True):
+        llm = LLM(
+            model="openrouter/deepseek/deepseek-chat", response_format=DummyResponse
+        )
+        # Should not raise any error.
+        llm._validate_call_params()
+
+
+def test_validate_call_params_not_supported():
+    class DummyResponse(BaseModel):
+        a: int
+
+    # Patch supports_response_schema to simulate an unsupported model.
+    with patch("crewai.llm.supports_response_schema", return_value=False):
+        llm = LLM(model="gemini/gemini-1.5-pro", response_format=DummyResponse)
+        with pytest.raises(ValueError) as excinfo:
+            llm._validate_call_params()
+        assert "does not support response_format" in str(excinfo.value)
+
+
+def test_validate_call_params_no_response_format():
+    # When no response_format is provided, no validation error should occur.
+    llm = LLM(model="gemini/gemini-1.5-pro", response_format=None)
+    llm._validate_call_params()
+
+
 @pytest.mark.vcr(filter_headers=["authorization"])
 def test_o3_mini_reasoning_effort_high():
     llm = LLM(