Key Takeaways
- MCP auth for an Android SMS gateway is the same Bearer token REST uses — loaded from the wrapper’s environment, never from the model.
- This is not a first-party Cursor/Claude plugin login. Hosts spawn your process; you inject env.
- Least privilege: a send-capable key is not required to list docs. Prefer staging until the tool surface is narrow.
- Confirm live auth in Developer Center. Dashboard keys live at app.sms-gateway.app.
- You bring the phone and operator credit. Platform pricing is devices plus send volume.
The key is for HTTPS, not the chat
Concepts: MCP for SMS. Spec: Model Context Protocol. Live JSON: Developer Center. Dashboard: app.sms-gateway.app.
Hosts: Cursor, Claude Desktop. We meter devices and volume.
Bearer in the wrapper process
Authorization: Bearer on every call to https://app.sms-gateway.app/api/v1. MCP may add its own host↔server auth later; that is not a substitute for the gateway key.
“If the model can print the key, the key is already gone. Env, rotate, least tools — that is the whole walkthrough.”
Auth failure modes
| Symptom | Likely cause | First check |
|---|---|---|
| 401 | Host env not passed to child | Print env names (not values) in server logs |
| Key in transcript | Tool arg / user pasted | Rotate; strip from tool schema |
| Key in git | mcp.json literal | gitignore; env reference |
| Prod send from a demo | One key for all hosts | Staging key on laptops |
| Works in cURL, fails in MCP | Different key | Developer Center |
Split staging and send
Laptop hosts get staging. Production send stays in your backend. Keys in env. Pairing: setup.
Rotate like any other secret
Webhooks use a different HMAC secret — do not reuse the Bearer. Webhooks. Pricing.
Next steps
Create a staging key. Wire it only via env. Send one staff SMS. Operator credit stays yours.
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
- device setup guidePair and go live
- download the Android gateway appGet the APK
