Build variables, what they are meant for?

Hello, im trying to get some repository informations like Differential revision ID etc…
And my question is that variables are available to buildkite, if not how can i retrieve this informations?

These variables are available for the fields in the form above them. For example, in the “make HTTp call” step, you can enter something like this into the URL field:

http:/buildkite/start/?revision=${buildable.revision}

and this will resolve using the relevant revision ID (if applicable).