...

In order to access the TOTP API you need its client ID for the scope parameter of the OAuth2 Token Request. This client ID is visible in System → TOTP API → Applications → TOTP API as depicted here

Verify the API works

The following examples use non-existing TOTP authentication method in SSO with name non.existing.method.

You can start testing the connection using curl. You may use the --insecure flag in case self-signed certificates are used:

$ curl \
  --insecure \ 
  --request PUT 'https://<sso-base-url>/totp/api/v1/methods/non.existing.method' \
  --header 'Content-Type: application/json' \
  --data-raw '
  {
    "user": {
      "login": "any.user"
    }
  }'

...