Key Takeaways
- create_webhook via MCP (security): registering a callback is admin-shaped. HMAC secret + HTTPS URL allowlist. Agents should not point webhooks at arbitrary hosts.
- Same REST as the Android SMS gateway API. Confirm live webhook fields in Developer Center.
- Not a first-party plugin. Not an exploit guide. No PoCs.
- DLR retries must update a row, not originate a second SMS.
- Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Free is 300 SMS lifetime.
- Overview sibling: building an SMS MCP server (security).
MCP education: mcp for sms — create_webhook via MCP (security). Overview: MCP server overview. HTTP depth: server webhook in-depth. Laravel mapping: parse DLR. Product: webhooks.
Priced by devices and SMS send volume. You use your own phone and operator SMS credit.
A webhook URL is a mailbox. If the agent chooses the address, you just mailed customer numbers to a stranger.
create_webhook is a privilege
list_devices is inventory. create_webhook changes where events go. Default it off for chat sessions. Confirm the live create/list/delete fields in Developer Center — this page does not dump them.
Secret and URL allowlist
- HTTPS only.
- Host allowlist in your wrapper, not “whatever the model typed.”
- Secret rotated like an API key. Server keys in env.
Risk table: who may call the tool
| Caller | create_webhook | Why |
|---|---|---|
| Untrusted chat | Deny | Callback exfil |
| On-call with approval | Allowlisted hosts | Ops change with audit |
| CI / IaC | Fixed URL from env | No model in the loop |
| Send tool | Never combined blindly | Two privileges stacked |
Limits: webhooks limits.
Do not send from the webhook handler
Delivery events update state. They do not POST send. Same rule as Laravel DLR. OTP timeouts are independent of missing callbacks.
No callback-exfil recipes
We will not walk through spoofing signatures or tunneling payloads. If verification fails, drop the request.
A bad URL still spends ops time
Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Mis-aimed webhooks do not refund airtime; they leak metadata. Rotate secrets if a URL was wrong.
Checklist
- Tool off by default.
- HTTPS allowlist.
- HMAC env secret.
- Audit log of URL changes.
- No send in the receiver.
- Developer Center fields.
- No plugin claim.
- No PoC content.
- Idempotent event ids.
- STOP still writes suppression.
Next steps
Pair with list_devices and pricing. Callbacks are plumbing. Privilege is the point.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- SMS webhook integrationInbound and status events
- SMS API documentationLive endpoint reference
- device and SMS volume pricingPlans and allowances
- Security and Trust CenterCompliance and posture
