Looking at the API documentation, it mentions
IMPORTANT
Endpoint Prefix: All REST APIs in SysON start with /api/rest/ .
Looking at the example create_project.py in the APIs cookbook suggests that the endpoint for PUT and POST are not prefixed, and this is supported by the #828 changelog.
I would like to see the documentation (the snippet at the top of API Details explaining the endpoint prefix and the swagger API rendering below) reflect the endpoint. Preferably, the endpoint at /projects/ is also aliased to /api/rest/projects/ so that it can remain constant across the API