mts_id — operator-asserted (dual path)

The key trait: mts_id has two paths, and you don't know in advance which fires. Usually the operator confirms right on the SIM — and no code is needed. But if the push can't complete (e.g. an MVNO number), it falls back to SMS-OTP, and only then does the user get a code to enter.

So don't show a code input up front. Wait for the signal: the verification.code_required webhook or the awaiting_code: true flag in the status. No signal → no code.

What to watch for

• Poll awaiting_code (or listen for verification.code_required) — show the code input only on that signal. Before it, awaiting_code: false.
• /v1/verify/check is asynchronous. We relay the code to the operator, and the final result arrives a moment later — so the check response is status: sent, not verified. Learn the outcome from GET /v1/verify/{request_id} or the verification.verified / verification.failed / verification.expired webhooks (an operator-consent timeout arrives as expired).
• A code submitted too early (before the fallback) returns 409 not_pending.