[CI][Frontend] Return 422 instead of 500 for invalid Anthropic tool_choice (#34590)

Signed-off-by: Andreas Karatzas <akaratza@amd.com>

tests/entrypoints/openai/test_openai_schema.py

@@ -151,6 +151,7 @@ def test_openapi_stateless(case: schemathesis.Case):
         # requires a longer timeout
         ("POST", "/v1/chat/completions"): LONG_TIMEOUT_SECONDS,
         ("POST", "/v1/completions"): LONG_TIMEOUT_SECONDS,
+        ("POST", "/v1/messages"): LONG_TIMEOUT_SECONDS,
     }.get(key, DEFAULT_TIMEOUT_SECONDS)
 
     # No need to verify SSL certificate for localhost

vllm/entrypoints/anthropic/protocol.py

@@ -5,7 +5,7 @@
 import time
 from typing import Any, Literal
 
-from pydantic import BaseModel, field_validator
+from pydantic import BaseModel, field_validator, model_validator
 
 
 class AnthropicError(BaseModel):
@@ -76,6 +76,12 @@ class AnthropicToolChoice(BaseModel):
     type: Literal["auto", "any", "tool"]
     name: str | None = None
 
+    @model_validator(mode="after")
+    def validate_name_required_for_tool(self) -> "AnthropicToolChoice":
+        if self.type == "tool" and not self.name:
+            raise ValueError("tool_choice.name is required when type is 'tool'")
+        return self
+
 
 class AnthropicMessagesRequest(BaseModel):
     """Anthropic Messages API request"""