The ALMA Observing Tool (OT) is the software application used to prepare 
and submit ALMA observing proposals. It is designed to capture all the
information needed in order to evaluate, schedule and execute 
the observations proposed. During the Phase I process prospective PIs 
use the OT to define their proposed observations in terms of a set of 
Science Goals, which contain details on the science targets as well as 
the array and correlator setup, calibration, and sensitivity 
requirements. The OT users are aided by built-in interactive tools such 
as the sensitivity calculator, the spectral line picker and the field 
setup editor. If the proposal is successful, the OT is again used in 
Phase II to prepare the Scheduling Blocks, which contain all the 
technical parameters for execution at the telescope.
I will present a general overview of this versatile and powerful tool 
and explain concepts such as Science Goals and sensitivity-based 
observing requests, which are fundamental to ALMA Science Operations.