Courier

The Model

Courier is a notification platform. One API sends your product's notifications on email, SMS, push, in-app inbox, Slack, Microsoft Teams and WhatsApp through provider accounts you connect (SendGrid, Amazon SES, Twilio, FCM, APNs and more), with templates, journeys, preferences, brands, tenants, broadcasts, logs and analytics in one place. Teams edit templates in Design Studio without a deploy. A workspace has environments (Production, Test, and custom ones), each with its own API keys, templates and logs, and the key on a request picks the environment.

One send call does the whole job. You address a user (or list, audience, or tenant), content comes from a template or inline, routing picks the channels, and preferences gate delivery. Courier renders, routes, and delivers; your app supplies the trigger and the data.

Multi-step flows (anything with a delay, a branch, or aggregation) are journeys, defined as JSON and invoked by API.

How to Use This Skill

Route first. Where to Look picks the 1–2 files for the task. Don't read the tree.
Ask when the request is ambiguous. Channel? Transactional or lifecycle? New code or existing? Which language? Skip the questions when the request is already specific.
Verify shapes against a live source rather than memory. The installed SDK's own types are ground truth.
Apply the rules. Universal Rules and each file's Quick Reference are constraints, not suggestions. (sdk-reference.md is a lookup table and has none.)

If the project already has @trycourier/courier or trycourier installed, skip quickstart's install steps and assume client exists.