diff --git a/catalog.yaml b/catalog.yaml
index f12620c..f8dcee0 100644
--- a/catalog.yaml
+++ b/catalog.yaml
@@ -158,6 +158,9 @@ apps:
       config.json (Focalboard reads DB settings from /opt/focalboard/config.json
       inside the container, NOT from environment variables). README in ts-focalboard
       documents the postgres setup.
+      serve.headscale.json uses the actual MagicDNS base domain
+      (focalboard.damconsulting.net), not a {{service}} placeholder, because
+      tailscale serve does NOT substitute template variables in JSON values.
 
   - service: freshrss
     display_name: FreshRSS