Developers 15 October 2026 7 min read

Bulk SMS API in Kenya: A Developer's Guide

If you are sending SMS from an application, OTPs at signup, order updates, payment alerts, you need an API, not a web form. Here is what separates a good bulk SMS API in Kenya from a frustrating one, and how to integrate one the right way.

What to look for in an SMS API

• Simple auth. A bearer API key in a header. No SOAP, no XML, no bespoke signing just to send a message.
• Predictable JSON. Clear request and response bodies, standard HTTP status codes.
• Delivery reports. Webhooks that tell you what landed, so you are not polling or guessing.
• Idempotency. A way to retry safely without sending, or charging, twice.
• A real SDK. A typed library so you are not hand-rolling HTTP calls.
• Honest docs. A quickstart that works from a fresh machine, with runnable examples.

Many Kenyan providers miss most of this list. They bolt a thin API onto a dashboard and call it done. That is the gap worth avoiding.

Sending a message

A good send is one HTTP call. With PESA RAILS it looks like this:

curl https://api.sms.pesarails.com/v1/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "to": "254712345678", "sender": "PESARAILS", "message": "Your code is 4821" }'

Or with the SDK:

import { Pesarails } from "@pesarails/sms";
const sms = new Pesarails(process.env.PESARAILS_KEY);
await sms.send({ to: "254712345678", sender: "PESARAILS", message: "Your code is 4821" });

Common integration mistakes

1. No idempotency on OTPs. A timeout plus a retry sends two codes. Always pass an idempotency key.
2. Polling for delivery. Register a webhook instead and let the status come to you.
3. Hardcoding the sender. Keep your sender ID and key in environment variables.
4. Ignoring segments. Messages over 160 characters cost more than one SMS. Count before you send.

Going further

The full reference, authentication, bulk sending, webhooks and error handling, is in our developer docs. You can send your first message in about five minutes.