diff --git a/server/cmd/server/main.go b/server/cmd/server/main.go
index b9f1442..3c82344 100644
--- a/server/cmd/server/main.go
+++ b/server/cmd/server/main.go
@@ -55,6 +55,14 @@ func main() {
 	})
 
 	// --- Probe ingest route (optional) ---
+	// Requires:
+	//   PROBE_SECRETS  – JSON object mapping probeId → HMAC secret, e.g.
+	//                    '{"probe-sg-01":"s3cr3t1","probe-jp-01":"s3cr3t2"}'
+	//   REDIS_ADDR     – Redis address, default 127.0.0.1:6379
+	//   REDIS_PASSWORD – Redis password (optional)
+	//
+	// If PROBE_SECRETS is empty the route is not registered and the server
+	// starts normally without the probe ingest endpoint.
 	probeSecretsJSON := os.Getenv("PROBE_SECRETS")
 	if probeSecretsJSON != "" {
 		redisAddr := getenvDefault("REDIS_ADDR", "127.0.0.1:6379")