The "&{tracker}" syntax requires a selected token, but messages generated by sendChat don't have selected tokens. However, you can add to the tracker yourself in one of two ways: 1) Pass a callback to sendChat, in which you grab the results of the roll you made and put the relevant token into the tracker wherever you want. When you pass a callback to sendChat, it doesn't display the message in the chat, so you'll have to make your own output if you want it. 2) Make the output of your sendChat unique enough that you can catch it in a global "chat:message" handler, in which you grab the results of the roll you generated and put the relevant token into the tracker. If you go this route, you'll probably want to put something into state that says you have a roll outstanding for a particular token (ideally including the entire command you sent so you can match against it in your "chat:message" handler) so that you don't accidentally grab arbitrary rolls sent by players or other scripts.
