When sending messages, you can either send messages to an array of chats, or send directly to one chat. Bulk endpoints are separate from direct endpoints.
GET /chats/:chatID/messagesGets the most recent messages from a chat
POST /chats/:chatID/messagesSends a message to a given chat
POST /chats/:chatID/messages/pluginSends a plugin message to a given chat
The bulk API extends upon the previous two endpoints and allows you to send the same message to multiple chats without making multiple API calls. Their request and response payloads are the same, but require the following query-string parameters