feat: support tool_choice = {required, none, <function>} (#1059)

Summary:

titled


Test Plan:

added tests and

LLAMA_STACK_CONFIG=fireworks pytest -s -v tests/client-sdk/
--safety-shield meta-llama/Llama-Guard-3-8B

tests/client-sdk/agents/test_agents.py

@@ -98,7 +98,6 @@ def agent_config(llama_stack_client, text_model_id):
             },
         },
         toolgroups=[],
-        tool_choice="auto",
         input_shields=available_shields,
         output_shields=available_shields,
         enable_session_persistence=False,
@@ -322,6 +321,38 @@ def test_custom_tool(llama_stack_client, agent_config):
     assert "get_boiling_point" in logs_str
 
 
+def test_tool_choice(llama_stack_client, agent_config):
+    data = [
+        ("required", '{"type": "function"'),
+        ("none", None),
+        ("get_boiling_point", '{"type": "function", "name": "get_boiling_point"'),
+    ]
+    client_tool = TestClientTool()
+    for tool_choice, expected_tool in data:
+        agent_config["tool_config"] = {"tool_choice": tool_choice}
+        agent_config["client_tools"] = [client_tool.get_tool_definition()]
+
+        agent = Agent(llama_stack_client, agent_config, client_tools=(client_tool,))
+        session_id = agent.create_session(f"test-session-{uuid4()}")
+
+        response = agent.create_turn(
+            messages=[
+                {
+                    "role": "user",
+                    "content": "What is the boiling point of polyjuice?",
+                },
+            ],
+            session_id=session_id,
+        )
+
+        logs = [str(log) for log in EventLogger().log(response) if log is not None]
+        logs_str = "".join(logs)
+        if expected_tool:
+            assert expected_tool in logs_str
+        else:
+            assert '{"type": "function"' not in logs_str
+
+
 # TODO: fix this flaky test
 def xtest_override_system_message_behavior(llama_stack_client, agent_config):
     client_tool = TestClientTool()

tests/client-sdk/inference/test_text_inference.py

@@ -247,6 +247,42 @@ def test_text_chat_completion_with_tool_calling_and_streaming(
     assert tool_invocation_content == "[get_weather, {'location': 'San Francisco, CA'}]"
 
 
+def test_text_chat_completion_with_tool_choice_required(
+    llama_stack_client, text_model_id, get_weather_tool_definition, provider_tool_format, inference_provider_type
+):
+    if inference_provider_type == "remote::vllm":
+        pytest.xfail("vllm-project/vllm#13002")
+    response = llama_stack_client.inference.chat_completion(
+        model_id=text_model_id,
+        messages=[
+            {"role": "system", "content": "You are a helpful assistant."},
+            {"role": "user", "content": "What's the weather like in San Francisco?"},
+        ],
+        tools=[get_weather_tool_definition],
+        tool_config={"tool_choice": "required", "tool_prompt_format": provider_tool_format},
+        stream=True,
+    )
+    tool_invocation_content = extract_tool_invocation_content(response)
+    assert tool_invocation_content == "[get_weather, {'location': 'San Francisco, CA'}]"
+
+
+def test_text_chat_completion_with_tool_choice_none(
+    llama_stack_client, text_model_id, get_weather_tool_definition, provider_tool_format
+):
+    response = llama_stack_client.inference.chat_completion(
+        model_id=text_model_id,
+        messages=[
+            {"role": "system", "content": "You are a helpful assistant."},
+            {"role": "user", "content": "What's the weather like in San Francisco?"},
+        ],
+        tools=[get_weather_tool_definition],
+        tool_config={"tool_choice": "none", "tool_prompt_format": provider_tool_format},
+        stream=True,
+    )
+    tool_invocation_content = extract_tool_invocation_content(response)
+    assert tool_invocation_content == ""
+
+
 def test_text_chat_completion_structured_output(llama_stack_client, text_model_id, inference_provider_type):
     class AnswerFormat(BaseModel):
         first_name: str