Document reply markup limits

telethon/client/messages.py

@@ -418,6 +418,14 @@ class MessageMethods(UploadMethods, ButtonMethods, MessageParseMethods):
                 you have signed in as a bot. You can also pass your own
                 :tl:`ReplyMarkup` here.
 
+                All the following limits apply together:
+
+                * There can be 100 buttons at most (any more are ignored).
+                * There can be 8 buttons per row at most (more are ignored).
+                * The maximum callback data per button is 64 bytes.
+                * The maximum data that can be embedded in total is just
+                  over 4KB, shared between inline callback data and text.
+
             silent (`bool`, optional):
                 Whether the message should notify people in a broadcast
                 channel or not. Defaults to ``False``, which means it will

telethon_generator/data/error_descriptions

@@ -68,3 +68,5 @@ TAKEOUT_INIT_DELAY_X=A wait of {} seconds is required before being able to initi
 CHAT_NOT_MODIFIED=The chat or channel wasn't modified (title, invites, username, admins, etc. are the same)
 URL_INVALID=The URL used was invalid (e.g. when answering a callback with an URL that's not t.me/yourbot or your game's URL)
 USER_NOT_PARTICIPANT=The target user is not a member of the specified megagroup or channel
+TAKEOUT_REQUIRED=You must initialize a takeout request first
+REPLY_MARKUP_TOO_LONG=The data embedded in the reply markup buttons was too much