start_2fa

holdings.proof/mcp-server · Verify this server

Start a two-factor authentication challenge for a sensitive operation. Sends a verification code via the chosen channel. Returns a session ID, and for messaging channels: deep_link, qr_code (base64 PNG), and qr_text (UTF-8 text QR for terminal display). Agent usage — full 2FA flow: (1) Call start_2fa with the appropriate action_type and channel. (2) Present the challenge, and do NOT announce a message the server did not send: email is the ONLY channel it dispatches on. On telegram/whatsapp the user opens `deep_link` and sends the message themselves; on sms they send `sms_message` to a number from `sms_dids`; the response's own `instructions` field says which. On email, a 200 carrying `requires_email_selection: true` and `available_emails` means nothing was sent and no session exists — ask which address and call again with `email_id`. For telegram/whatsapp, pass `deep_link` to render_auth_link; for sms, show `sms_message`. Never hand `qr_text` to a link renderer — it is the link already rendered as QR art, so print it verbatim inside a fenced code block only when a real terminal needs the QR. (3) Poll get_2fa_status with the returned session_id until status is "verified" (the user enters the code on their device) or "expired". (4) If verified, proceed with the protected operation (e.g. create_api_key). If expired, inform the user and offer to restart. Typical channels: "telegram" or "email". For email, the user may receive a magic link instead of a code — the backend handles this automatically. ACCESS: needs a Proof account. Authenticate this client (Claude Code: /mcp → Authenticate), or sign in with start_login — a session opens this tool — then call this tool again.