diff --git a/tools/metrics.py b/tools/metrics.py
index d716cb2a5..0e29fc1ab 100644
--- a/tools/metrics.py
+++ b/tools/metrics.py
@@ -384,9 +384,9 @@ def render_combine_table(json_data, sort_order='name+'):
 def write_combine_markdown(json_data, path, sort_order='name+', title="TinyUSB Average Code Size Metrics"):
     """Write averaged size data to a markdown file."""
 
-    md_lines = [f"## {title}", ""]
+    md_lines = [f"## {title}", "", "<details><summary>Size table</summary>", ""]
     md_lines.extend(render_combine_table(json_data, sort_order))
-    md_lines.append("")
+    md_lines.extend(["", "</details>", ""])
 
     if json_data.get("file_list"):
         md_lines.extend(["<details>", "<summary>Input files</summary>", ""])