diff --git a/docs/csaf_aggregator.md b/docs/csaf_aggregator.md
index e9b3bf1..8a6bf84 100644
--- a/docs/csaf_aggregator.md
+++ b/docs/csaf_aggregator.md
@@ -92,6 +92,8 @@ aggregator            // table with basic infos for the aggregator object
 providers             // array of tables, each entry to be mirrored or listed
 ```
 
+At least 2 providers have to be configured. The other options are optional.
+
 Rates are specified as floats in HTTPS operations per second.
 0 means no limit. The rates can be specified per provider. Any provider
 which has no specified rate will use the configured default. If
@@ -108,6 +110,9 @@ category
 update_interval
 ```
 
+Any provider needs a valid name and domain. The other
+options are optional.
+
 If you want an entry to be listed instead of mirrored
 in a `aggregator.category == "aggregator"` instance,
 set `category` to `lister` in the entry.