Key Takeaways
- Wait-for-OTP agent flows poll or await your app’s verification state — they must never read plaintext OTP from SMS tools or transcripts.
- MCP is a REST/tool wrapper around the Android SMS gateway, not a marketplace plugin that owns the radio.
- Send OTP, wait with backoff, then verify via your store — accept ≠ delivered ≠ verified.
- Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Free is 300 SMS lifetime — agent retries burn airtime.
- Keys in ENV; rate-limit wait loops; isolate OTP devices from promo.
- Confirm live send fields in Developer Center.
Summary
This setup walkthrough covers a wait-for-OTP agent flow with an MCP server in front of an Android SMS gateway. MCP wraps REST — it is not a plugin that replaces pairing or airtime. Priced by devices and SMS send volume. You use your own phone and operator SMS credit.
If the agent “waits” by printing the code it just sent, you automated self-approval. Wait for the user (or your verifier) — not for the model to peek.
What wait-for-OTP means
After send_otp, the agent polls your verification_status (or awaits a webhook your app recorded) until success, failure, or timeout. The Android phone only handles the SMS send via gateway REST — see SMS API documentation.
Agent steps table
| Step | Tool / API | Must not |
|---|---|---|
| Send | MCP → gateway REST | Return plaintext OTP |
| Wait | Poll app status w/ backoff | Busy-loop without caps |
| Verify | App verify_otp store | Read SMS body into model |
| Timeout | Expire challenge | Blind resend storms |
Setup walkthrough
- Implement OTP store + verify API in your backend.
- Expose MCP tools: send (REST wrapper), status/wait, verify — ENV secrets only.
- Cap wait polls (e.g. every 2–5s, max 2–5 minutes).
- Idempotent resend with attempt limits.
- Canary staff flow; watch device last-seen.
Timeouts and polling
Radio delay is not HTTP delay. Pending age on the handset can exceed agent impatience. Raise OEM SMS ceilings only where allowed; carrier fair-use still applies. Pair via setup.
Cost
Free is 300 SMS lifetime. Resends spend airtime. See pricing.
Checklist
- MCP = REST wrapper, not plugin storefront.
- No OTP in transcripts; wait capped; OTP devices isolated.
- Canary passed before production agents.
Next steps
See OTP verification and keep redaction on every tool result.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- OTP and 2FA SMS on AndroidAuthentication flows
- SMS API documentationLive endpoint reference
- device and SMS volume pricingPlans and allowances
- device setup guidePair and go live
