Key Takeaways
- send_sms MCP tool design is a thin REST send: to, body, idempotency_key → message_id — not a Cursor plugin.
- Require list_devices first. Keys in env. Never return or echo OTP/secrets in tool output.
- Keep bulk as a separate, human-gated tool — or omit it from agent hosts.
- This page is prompt + contract. Live fields live in Developer Center. No MCP source dump.
- Do not confuse with send_otp / verify_otp — those keep digits hashed.
- You bring the Android and operator credit. We meter devices and send volume.
Tight send_sms contract
send_sms MCP tool design — example agent prompt defines the general send tool for your REST wrapper over a paired Android. Overview: MCP overview. Security: securing SMS MCP tools.
A send tool without idempotency is a footgun with prepaid minutes attached.
Example agent prompt
“Call list_devices first. send_sms only with to, body, and idempotency_key. Return message_id/status — not secrets. Honor 429. Never invent recipients. Never echo OTP-like bodies into chat.” Spec: MCP specification. Fields: Developer Center.
Args and returns
| Field | Required? | Rule |
|---|---|---|
| to | Yes | User-named E.164; no CRM dumps |
| body | Yes | Do not log/echo if OTP-like |
| idempotency_key | Yes | Stable per user intent |
| message_id | Return | Enough for DLR follow-up |
Not the OTP pair
For authentication flows use send_otp / verify_otp tools. Product: OTP verification.
Cost
You bring the Android and operator SMS credit. Duplicate sends without idempotency still meter volume. Free: 1 device / 300 SMS lifetime / 300 contacts. See device and SMS volume pricing.
Checklist
- Contract documented; no bulk on agent host.
- Idempotency required.
- list_devices gate.
- Keys in env.
- No OTP echo.
- No plugin claim.
- No MCP source dump.
- Developer Center for live fields.
Next steps
Primer: What is MCP for SMS. Errors: MCP error-handling prompt.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- SMS API documentationLive endpoint reference
- device and SMS volume pricingPlans and allowances
- Android SMS gateway product guideDefinition, product, and how to buy
- download the Android gateway appGet the APK
