diff --git a/core/config/backend_config.go b/core/config/backend_config.go
index 1eb2fcbf067..660d257166d 100644
--- a/core/config/backend_config.go
+++ b/core/config/backend_config.go
@@ -172,7 +172,12 @@ func (c *BackendConfig) ShouldCallSpecificFunction() bool {
 }
 
 func (c *BackendConfig) FunctionToCall() string {
-	return c.functionCallNameString
+	if c.functionCallNameString != "" &&
+		c.functionCallNameString != "none" && c.functionCallNameString != "auto" {
+		return c.functionCallNameString
+	}
+
+	return c.functionCallString
 }
 
 func (cfg *BackendConfig) SetDefaults(opts ...ConfigLoaderOption) {
diff --git a/core/config/backend_config_loader.go b/core/config/backend_config_loader.go
index 5d1df2694f7..c1fed818726 100644
--- a/core/config/backend_config_loader.go
+++ b/core/config/backend_config_loader.go
@@ -381,7 +381,13 @@ func updateBackendConfigFromOpenAIRequest(bc *BackendConfig, request *schema.Ope
 
 	if request.ToolsChoice != nil {
 		var toolChoice grammar.Tool
-		json.Unmarshal([]byte(request.ToolsChoice.(string)), &toolChoice)
+		switch content := request.ToolsChoice.(type) {
+		case string:
+			_ = json.Unmarshal([]byte(content), &toolChoice)
+		case map[string]interface{}:
+			dat, _ := json.Marshal(content)
+			_ = json.Unmarshal(dat, &toolChoice)
+		}
 		request.FunctionCall = map[string]interface{}{
 			"name": toolChoice.Function.Name,
 		}