Hi Mike,
We have a helper method for obtaining the available statuses in the project schema, but it doesn't seem to be one for returning the available types at the moment.
It is a bit complicated to follow the entity structure for the project/workflow schemas, so I did a first pass at a similar method which you can find here: https://bitbucket.org/snippets/ftrack/n79e8B
It might need some more polish before it is read for general use, but I believe it should be enough for your use case. You can use it like so:
getAvailableTypes(
session,
'AssetBuild',
'caddd816-acb5-11e1-8668-f23c91df1211'
).then(
types => console.info('Types', types)
);
Regards,
Lucas