fix: strip unsupported Anthropic built-in tools before forwarding to vLLM

vLLM's /v1/messages requires input_schema on every tool, so Anthropic
built-in tools like web_search, computer_use, text_editor, and bash cause
400 validation errors. Filter them out in transform_anthropic_messages_request.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

litellm/llms/hosted_vllm/messages/transformation.py

@@ -102,6 +102,26 @@ class HostedVLLMAnthropicMessagesConfig(BaseAnthropicMessagesConfig):
             base = base[:-3]
         return f"{base}/v1/messages"
 
+    # Anthropic built-in tool types that vLLM does not support in /v1/messages
+    _UNSUPPORTED_TOOL_TYPES = frozenset({
+        "web_search",
+        "computer",
+        "text_editor",
+        "bash",
+    })
+
+    def _strip_unsupported_tools(self, tools: Optional[List[Dict]]) -> Optional[List[Dict]]:
+        """Remove Anthropic built-in tools (web_search, computer_use, etc.) that
+        vLLM's /v1/messages endpoint does not understand."""
+        if not tools:
+            return tools
+        return [
+            t for t in tools
+            if not isinstance(t, dict)
+            or t.get("type", "") not in self._UNSUPPORTED_TOOL_TYPES
+            and not t.get("type", "").startswith(tuple(f"{p}_" for p in self._UNSUPPORTED_TOOL_TYPES))
+        ]
+
     def transform_anthropic_messages_request(
         self,
         model: str,
@@ -114,6 +134,14 @@ class HostedVLLMAnthropicMessagesConfig(BaseAnthropicMessagesConfig):
         if max_tokens is None:
             raise ValueError("max_tokens is required for Anthropic /v1/messages API")
 
+        tools = self._strip_unsupported_tools(
+            anthropic_messages_optional_request_params.get("tools")
+        )
+        if tools:
+            anthropic_messages_optional_request_params["tools"] = tools
+        else:
+            anthropic_messages_optional_request_params.pop("tools", None)
+
         return {
             "model": model,
             "messages": messages,

tests/litellm/llms/hosted_vllm/test_anthropic_passthrough.py

@@ -148,6 +148,45 @@ class TestHostedVLLMConfig:
         assert "frequency_penalty" not in payload
         assert "presence_penalty" not in payload
 
+    def test_unsupported_tools_are_stripped(self):
+        """Anthropic built-in tools (web_search, computer_use, etc.) must be
+        removed because vLLM's /v1/messages requires input_schema on every tool."""
+        messages = [{"role": "user", "content": "search the web"}]
+        tools = [
+            {"type": "web_search_20250305", "name": "web_search", "max_uses": 8},
+            {"type": "computer_20250124", "name": "computer"},
+            {"type": "custom", "name": "my_tool", "input_schema": {"type": "object"}},
+        ]
+        optional_params = {"max_tokens": 100, "tools": tools}
+        payload = self.config.transform_anthropic_messages_request(
+            model="qwen",
+            messages=messages,
+            anthropic_messages_optional_request_params=optional_params,
+            litellm_params=GenericLiteLLMParams(),
+            headers={},
+        )
+        # Only the custom tool survives
+        assert payload["tools"] == [
+            {"type": "custom", "name": "my_tool", "input_schema": {"type": "object"}},
+        ]
+
+    def test_tools_key_removed_when_all_stripped(self):
+        """If all tools are unsupported, the tools key should be removed entirely."""
+        messages = [{"role": "user", "content": "hi"}]
+        tools = [
+            {"type": "web_search_20250305", "name": "web_search"},
+            {"type": "bash_20250124", "name": "bash"},
+        ]
+        optional_params = {"max_tokens": 100, "tools": tools}
+        payload = self.config.transform_anthropic_messages_request(
+            model="qwen",
+            messages=messages,
+            anthropic_messages_optional_request_params=optional_params,
+            litellm_params=GenericLiteLLMParams(),
+            headers={},
+        )
+        assert "tools" not in payload
+
     def test_request_payload_missing_max_tokens_raises(self):
         with pytest.raises(ValueError, match="max_tokens is required"):
             self.config.transform_anthropic_messages_request(