diff --git a/llama_stack/providers/remote/inference/vllm/vllm.py b/llama_stack/providers/remote/inference/vllm/vllm.py
index b37b0d305..d1793c524 100644
--- a/llama_stack/providers/remote/inference/vllm/vllm.py
+++ b/llama_stack/providers/remote/inference/vllm/vllm.py
@@ -34,6 +34,7 @@ from llama_stack.apis.inference import (
     ToolPromptFormat,
 )
 from llama_stack.apis.models import Model, ModelType
+from llama_stack.models.llama.datatypes import BuiltinTool
 from llama_stack.models.llama.sku_list import all_registered_models
 from llama_stack.providers.datatypes import ModelsProtocolPrivate
 from llama_stack.providers.utils.inference.model_registry import (
@@ -112,10 +113,16 @@ def _convert_to_vllm_tools_in_request(tools: List[ToolDefinition]) -> List[dict]
                 if tool_param.required:
                     compat_required.append(tool_key)
 
+        # The tool.tool_name can be a str or a BuiltinTool enum. If
+        # it's the latter, convert to a string.
+        tool_name = tool.tool_name
+        if isinstance(tool_name, BuiltinTool):
+            tool_name = tool_name.value
+
         compat_tool = {
             "type": "function",
             "function": {
-                "name": tool.tool_name,
+                "name": tool_name,
                 "description": tool.description,
                 "parameters": {
                     "type": "object",