Some agent-related functionality is not entirely complete. In particular, support for proxy agents, that advertise specific Diameter applications but otherwise relay messages in much the same way as relay agents (for which a handle_request/3 callback can return a relay tuple), will be completed in an upcoming release. There may also be more explicit support for redirect agents, although redirect behaviour can be implemented with the current functionality.

There is some asymmetry in the treatment of messages sent as diameter_header/avp records and those sent in the "normal" fashion, and not all of this is documented. This is related to the previous point since this form of sending a message was introduced specifically to handle relay agent behaviour using the same callback interface as for client/server behaviour.

The User's Guide is currently quite thin. The introductory chapter followed by the examples (in the application examples subdirectory) may be sufficient for those having some familiarity with the Diameter protocol but the intention is to provide more introductory text. The reference documentation is quite complete, although some points could likely be expanded upon.

The function diameter:service_info/2 can be used to retrieve information about a started service (statistics, information about connected peers, etc) but this is not yet documented and both the input and output may change in the next release.