diff --git a/internal/llm/provider/anthropic.go b/internal/llm/provider/anthropic.go
index 18767b56ec04f2615c57931660772cc628ddda20..d7f678a9b82932356d15e423fe362aab15d521a8 100644
--- a/internal/llm/provider/anthropic.go
+++ b/internal/llm/provider/anthropic.go
@@ -169,6 +169,9 @@ func (a *anthropicClient) convertMessages(messages []message.Message) (anthropic
 }
 
 func (a *anthropicClient) convertTools(tools []tools.BaseTool) []anthropic.ToolUnionParam {
+	if len(tools) == 0 {
+		return nil
+	}
 	anthropicTools := make([]anthropic.ToolUnionParam, len(tools))
 
 	for i, tool := range tools {