Documentation

Everything you need to plug your SaaS into Letter: report users and events from your backend, capture leads with forms, then drive sequences and broadcasts off of them.

Getting started

Agent setup Hand this to your coding agent: install, authenticate, instrument in one pass Read → Initial import Bulk-load existing users and accounts from your SaaS in one shot Read →

Guides

Forms Capture external leads with hosted, embeddable forms: fields, double opt-in, target lists, spam protection, the submit-to-sequence flow, and managing forms from the CLI and Management API Read → Sequences Author drip sequences end to end: triggers, the node graph, branch logic, email bodies, validation, and a full worked example for the CLI and Management API Read → Broadcasts Send a one-off email to a segment: build an audience from traits, events, and lists, preflight the recipient count, schedule or send now, and track delivery live, from the dashboard, CLI, or Management API Read →

API

Ingestion API identify · group · track · batch · auth · rate limits Read → Management API control-plane for projects, contacts, segments, sequences, broadcasts, templates, and settings Read →

SDKs

SDKs Official server-side clients for Node, Python, and Ruby. Same ingestion API, idiomatic in each language, with batching, retries, and idempotency built in. Read → Node SDK Auto-batching client for Node.js with retries and idempotency Read → Python SDK Auto-batching client for Python with retries and idempotency Read → Ruby SDK Auto-batching client for Ruby with retries and idempotency Read →

Command line

CLI letter login, and resource commands for projects, contacts, segments, lists, forms, sequences, broadcasts, templates, and settings Read →