So I removed "disabled":"false" and I am now getting through. This should be a clearer error message - the JSON is valid but perhaps the content is not?
Ah ok that seems to work. However, I am now struggling with 501 or 502 responses, e.g. with the above request I get:
HTTP/1.1 502 Bad Gateway
Content-Type: application/json
Server: Couchbase Sync Gateway/1.4.0
Date: Wed, 16 Aug 2017 11:33:11 GMT
Content-Length: 265
{"error":"Bad Gateway","reason":" Unable to connect to Couchbase Server (connection refused). Please ensure it is running and reachable at the configured host and port. Detailed error: HTTP error 401 Unauthorized getting \"http://couchbase-server:8091:/pools\": "}#
couchbase-server is the name given to the docker container running Couchbase Server.