Database Merge tool
Cbattlegear is correct - the process is not yet integrated into a single tool. Currently the Split/Merge tool only handles the data movement operations. However there is a Powershell example of orchestrating the entire process - including provisioning the target databases, adding it to the shard map, and invoking the split/merge operations. You can find it described in the testing section of the Split/Merge Tutorial.
Some customer simplify the process even further by maintaining an empty "golden copy" database containing all schema objects necessary for shards. Then when a new shard is needed, they perform a CREATE DATABASE AS COPY command to quickly create a new DB from the reference copy. This step can be scripted as well.
Finally, in addition to Powershell, there is a .Net API available for Split-Merge that allows the tool's operations to be integrated with other steps or APIs inside a C# executable. The API is included in the Split/Merge Nuget package and documented here.