SLSmartletter API

Introduction

Run your newsletter from code or from an AI agent.

The Smartletter API does what the dashboard does: write and send newsletter issues, manage contacts, collect signups from your own site, read stats, and send transactional email. The Smartletter MCP server offers the same actions to AI agents.

Base URL: https://api.smartletter.ai. Every request and answer is JSON, except image uploads and the CSV export.

Quick start

  • Create an API key in Settings → API keys.
  • Create a draft, review it, then send it.
curl -X POST https://api.smartletter.ai/newsletters \
  -H "Authorization: Bearer $SMARTLETTER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"subject":"This week in AI","markdown":"# Hello\n\nThree tools this week…"}'

curl -X POST https://api.smartletter.ai/newsletters/<id>/send \
  -H "Authorization: Bearer $SMARTLETTER_API_KEY" \
  -H "Content-Type: application/json" -d '{}'

Machine-readable