Letter CLI - connect your app to Letter in one command. Interactive, secure device login: no API key ever touches your shell or chat.
Official Node.js client for letter.app — onboarding email drip campaigns. Auto-batching, retries, idempotency.
Letter MCP server - give your AI agent tools to set up and verify a Letter integration. Reads the credential written by `letter login`; no secret in your MCP config.