diff --git a/router/src/infer/mod.rs b/router/src/infer/mod.rs
index f3b10450..efbaf480 100644
--- a/router/src/infer/mod.rs
+++ b/router/src/infer/mod.rs
@@ -336,8 +336,14 @@ impl ToolGrammar {
         tools: Option<Vec<Tool>>,
         tool_choice: Option<ToolType>,
     ) -> Result<Option<Tools>, InferError> {
-        if let Some((req_tools, tool_choice)) = tools.zip(tool_choice) {
-            // let tool_prompt = tool_prompt.unwrap_or_default();
+        if let Some(req_tools) = tools {
+            let tool_choice = tool_choice
+                .map(|t| match t {
+                    ToolType::FunctionName(name) if name == "auto" => ToolType::OneOf,
+                    _ => t,
+                })
+                .unwrap_or_default();
+
             let tools_to_use = match tool_choice {
                 ToolType::FunctionName(name) => {
                     vec![req_tools
diff --git a/router/src/lib.rs b/router/src/lib.rs
index f856406d..be02e645 100644
--- a/router/src/lib.rs
+++ b/router/src/lib.rs
@@ -840,12 +840,16 @@ fn default_tool_prompt() -> Option<String> {
     )
 }
 
-#[derive(Clone, Debug, Deserialize, PartialEq, Serialize, ToSchema)]
+#[derive(Clone, Default, Debug, Deserialize, PartialEq, Serialize, ToSchema)]
 #[serde(untagged)]
 pub enum ToolType {
+    #[default]
+    #[serde(alias = "auto")]
     OneOf,
     FunctionName(String),
-    Function { function: FunctionName },
+    Function {
+        function: FunctionName,
+    },
 }
 
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize, ToSchema)]