Thanks Martin... I did have the org_id, turns out the problem was that I missed that Tyk comes with 2 APIs, and I was trying to add the key using the one at api/keys with my admin user's secret.
I have now figured out that there is a different entry point (tyk/keys), running on a different port (8080 instead of 3000) and that requires the "secret id" from the tyk.conf file.
Having made the necessary changes, I have now moved on to a new error message
"error": "Failed to create key, ensure security settings are correct.",
Any idea what security settings should I check?
BTW, this command instead works fine with the same token.json file
curl -X POST http://localhost:8080/tyk/keys/create -H 'x-tyk-authorization: mysecretkey' -H 'Content-Type: application/json' -d @token.json
What still fails with the error message I mentioned above is this:
curl -X PUT http://localhost:8080/tyk/keys/abcde123456 -H 'x-tyk-authorization: mysecretkey' -H 'Content-Type: application/json' -d @token.json