Update README.md

README.md

@@ -25,6 +25,8 @@ If a payload with `fruits/apples` comes in, we would receive it. If a payload wi
 Event payloads requires that the IP or IP range (Ipv4 or IPv6) is listed in `pypubsub.yaml` under `payloaders` first.
 Once whitelisted, clients can do a POST or PUT to the pubsub service on port 2069, passing a JSON object as the request body, for instance: `curl -XPUT -d '{"foo": "bar"}' http://localhost:2069/some/topic/here`.
 
+Event payloads *MUST* be in dictionary (hash) format, or they will be rejected.
+
 ## Listening for events in PyPubSub via cURL
 You can subscribe to topics via cURL like so: `curl http://localhost:2069/topics/here` where `topics/here` are the topics you are subscribing to, with `/` as a delimiter between topics. To subscribe to *all* events, you can omit the topics.