diff --git a/core/config/backend_config.go b/core/config/backend_config.go
index 32e10a174367..db9c66654ddd 100644
--- a/core/config/backend_config.go
+++ b/core/config/backend_config.go
@@ -185,7 +185,12 @@ 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/http/endpoints/openai/request.go b/core/http/endpoints/openai/request.go
index 1f845c6f1cc1..c99812045ad8 100644
--- a/core/http/endpoints/openai/request.go
+++ b/core/http/endpoints/openai/request.go
@@ -146,7 +146,14 @@ func updateRequestConfig(config *config.BackendConfig, input *schema.OpenAIReque
 
 	if input.ToolsChoice != nil {
 		var toolChoice grammar.Tool
-		json.Unmarshal([]byte(input.ToolsChoice.(string)), &toolChoice)
+
+		switch content := input.ToolsChoice.(type) {
+		case string:
+			_ = json.Unmarshal([]byte(content), &toolChoice)
+		case map[string]interface{}:
+			dat, _ := json.Marshal(content)
+			_ = json.Unmarshal(dat, &toolChoice)
+		}
 		input.FunctionCall = map[string]interface{}{
 			"name": toolChoice.Function.Name,
 		}