diff --git a/src/azarrot/frontends/openai_frontend.py b/src/azarrot/frontends/openai_frontend.py
index f4e57f6..7ea8962 100644
--- a/src/azarrot/frontends/openai_frontend.py
+++ b/src/azarrot/frontends/openai_frontend.py
@@ -179,20 +179,32 @@ def __to_backend_generation_messages(
         return result
 
     def __to_backend_tool_parameters(
-        self, tool_parameters: list[dict[str, Any]] | None
+        self, tool_parameters: dict[str, Any] | None
     ) -> list[LocalizedToolParameter]:
         if tool_parameters is None:
             return []
 
-        return [
-            LocalizedToolParameter(
-                name=parameter["name"],
-                description=parameter.get("description"),
-                type=parameter["type"],
-                required=parameter.get("required", False),
-            )
-            for parameter in tool_parameters
-        ]
+        param_type = tool_parameters["type"]
+
+        if param_type != "object":
+            raise ValueError(f"Unsupported tool parameter type {param_type}")
+
+        required_params = tool_parameters.get("required", [])
+
+        params = []
+
+        if "properties" in tool_parameters:
+            for k, v in tool_parameters["properties"].items():
+                p = LocalizedToolParameter(
+                    name=k,
+                    description=v.get("description"),
+                    type=v.get("type"),
+                    required=k in required_params
+                )
+
+                params.append(p)
+
+        return params
 
     def __to_backend_tools_info(
         self, tools_info: list[ToolInfo] | None, tools_choice: Literal["none", "auto", "required"] | ToolChoice | None
diff --git a/src/azarrot/frontends/openai_support/openai_data.py b/src/azarrot/frontends/openai_support/openai_data.py
index 29f304f..67e4b8b 100644
--- a/src/azarrot/frontends/openai_support/openai_data.py
+++ b/src/azarrot/frontends/openai_support/openai_data.py
@@ -61,7 +61,7 @@ class ChatCompletionStreamOptions(BaseModel):
 class ToolFunctionInfo(BaseModel):
     description: str | None = None
     name: str
-    parameters: list[dict[str, Any]] | None = None
+    parameters: dict[str, Any] | None = None
 
 
 class ToolInfo(BaseModel):