This question asks the same thing and has an answer but not link to documentation:
Multiple sends through MessageDefinitionSends
Are you speaking of the Messaging/Send Endpoint?
The messageBatch resource allows you to send unique messages to
devices within the same API call. Each batch can include a maximum of
5000 subscriber key or device token values (depending on which value
the call uses).
All of the API documentation can be found Here
The current documentation shows the endpoint of:
Does this do the same thing as your endpoint (maybe your endpoint is depreciated??)
If you could be specific about the endpoint we could be more exact with an answer