Phone, SMS and voice agent API for developers

Developer guides

What can I build with the Call Bullet API?

You can add real UK telephony to an app without running your own carrier account: show tracked numbers, list calls with their marketing source, send texts with proof of delivery, create AI voice agents and let customers request a call back from a person.

Everything sits behind one base URL, https://callbullet.com/api/public/v1, and one bearer key that starts with cb_live_. Each key is scoped to the workspaces it may touch, and each product has its own permission, so a reporting dashboard never gains the power to send texts or place calls.

How fast can I get a first result?

Most developers read their first API response within five minutes of creating a key. A simulated text with test: true takes another minute and costs nothing. Real-world steps take longer because UK rules require them, and the guides say so plainly:

• UK numbers need business verification before activation, usually the same working day once documents are in.
• SMS sender names are reviewed by Call Bullet, usually within one working day. Until then you can send free live tests to a verified mobile.
• AI voice agents created through the API start as drafts. Testing, certification and billing are finished in Call Bullet before an agent takes real calls.
• Click-to-call works as soon as you have an active outbound line with a staff phone set, inside UK calling hours.

How do I make my first API call?

Create a key under Integrations → Developer API in Call Bullet, save it as a server-side secret called CALL_BULLET_API_KEY, and add this helper. Every guide reuses it.

// lib/call-bullet.server.ts — server-only. Never import this in browser code.
const BASE = "https://callbullet.com/api/public/v1";

export async function cb<T>(path: string, init: RequestInit = {}): Promise<T> {
  const key = process.env.CALL_BULLET_API_KEY; // cb_live_… stored as a secret
  if (!key) throw new Error("CALL_BULLET_API_KEY is not set");
  const res = await fetch(BASE + path, {
    ...init,
    headers: { Authorization: `Bearer ${key}`, "Content-Type": "application/json", ...init.headers },
  });
  const body = await res.json();
  if (!res.ok) throw new Error(`${res.status} ${body.error?.code}: ${body.error?.message}`);
  return body as T;
}

import { cb } from "./call-bullet.server";

const { data } = await cb<{ data: { id: string; name: string }[] }>("/workspaces");
console.log(data); // one entry per business the key can reach

Call the API only from server code, such as a server function or API route. A key in browser code can be copied by anyone who opens the page.

How do permissions keep the key safe?

Each product has read and write levels that you switch on per key. A key built for a call dashboard needs only workspaces:read and calls:read. A booking app that texts customers adds sms:send. The two most powerful writes, agents:write and calls:place, stay off even in the Everything preset, so they are only ever switched on deliberately.

Keys are stored only as hashes, shown once, and every request rechecks the workspace scope. See the scopes reference for the full list.

Can I paste one prompt into an AI app builder?

Yes. Each guide ends with a prompt you can paste into an AI app builder. This one connects any app to Call Bullet and stops before doing anything that costs money.

Connect this app to the Call Bullet API.
- Docs: https://callbullet.com/developers/api.md and https://callbullet.com/openapi.json. Use only endpoints listed there.
- Ask me for my Call Bullet API key (starts cb_live_) and store it as the server secret CALL_BULLET_API_KEY. Never put it in browser code.
- Create one server helper that calls https://callbullet.com/api/public/v1 with Authorization: Bearer <key> and surfaces error.code and error.message.
- Call GET /workspaces and show me the result on a simple settings page.
- Do not send texts, create agents or place calls until I ask.

Which guide should I start with?

Pick the outcome you want first; each guide stands on its own.

• Add a UK phone number to an AI-built app
• Send SMS from an AI-built app
• Add an AI voice agent to an AI-built app
• Add call tracking to an AI-built site
• Receive SMS delivery webhooks in an AI-built app
• Build a click-to-call button in an AI-built app
• Show call logs in an AI-built dashboard

The full reference lives at the Developer API docs, with an AI-readable copy at /developers/api.md and the OpenAPI file at /openapi.json.

Frequently asked questions