Start here
Quickstart
From no account to a sent message, in three calls.
Send your first email
One call, from an address that works before you verify a domain.
Sign in your first user
A code to an address, a session back, and a user that did not exist before.
Send your first text
One call, what segments cost, and why the first one is probably blocked.
Build with your stack
Next.js
Server-side sends, sign-in components, and a protected route handler.
Express and Node
One middleware, and req.lath is the signed-in user.
Hono, Workers and Bun
The edge runtimes, and the one import that needs Node.
Any other language
There is no SDK for yours yet. The HTTP call is four lines.
Every surface
The same operations, whichever way you reach them.REST
One POST per operation, and an OpenAPI document generated from the same definitions.
MCP
Every operation is a tool, with the input schema and the result schema an agent needs before it calls.
CLI
Generated, so a new operation is a new command the day it exists.
SDK
Typed in both directions: the input it takes and the result it returns.
Dashboard
A screen for every operation you’d do by hand, built on the same API a customer uses.
For agents
Hand the work to Claude Code, Codex or Cursor — they operate Lath directly.
Before you send to anybody real
Consent and suppression
The one gate every send passes, why email and SMS answer differently, and how to prove opt-in.
Spending caps
How a cap is enforced, and what a send does when it would cross one.
Domains and deliverability
The five DNS records, what each is for, and what actually decides whether mail arrives.
Reference
API reference
Every operation — 206 of them — with its schema and a request you can send.
Webhook events
158 events across 7 products, and the wildcard for each.
Error codes
142 refusals, by HTTP status, each carrying the fix.