The full documentation is a work in progress here:
https://toast-cmb.readthedocs.io/en/latest/
And is being overhauled for upcoming release 2.3.
There are two upcoming releases which include large changes. The first is 2.3:
https://github.com/hpc4cmb/toast/milestone/10
which includes a large internal refactor of the C++ code, the build system, and the python bindings. That will be followed by 2.4:
https://github.com/hpc4cmb/toast/milestone/11
which is focused on simplifying pipelines by instantiating operators from a simple config file format.