[BugFix] Support tool_choice=none in the Anthropic API (#35835)

Signed-off-by: ZhongsJie <zhongsjie@gmail.com>
Co-authored-by: Chauncey <chaunceyjiang@gmail.com>

vllm/entrypoints/anthropic/protocol.py

@@ -77,7 +77,7 @@ class AnthropicTool(BaseModel):
 class AnthropicToolChoice(BaseModel):
     """Tool Choice definition"""
 
-    type: Literal["auto", "any", "tool"]
+    type: Literal["auto", "any", "tool", "none"]
     name: str | None = None
 
     @model_validator(mode="after")

vllm/entrypoints/anthropic/serving.py

@@ -349,6 +349,8 @@ class AnthropicServingMessages(OpenAIServingChat):
             req.tool_choice = "auto"
         elif tool_choice_type == "any":
             req.tool_choice = "required"
+        elif tool_choice_type == "none":
+            req.tool_choice = "none"
         elif tool_choice_type == "tool":
             req.tool_choice = ChatCompletionNamedToolChoiceParam.model_validate(
                 {