Transactional Email Operations (SendGrid)

Use this skill to send transactional email through Twilio SendGrid and to diagnose delivery: bounces, spam complaints, and the Signed Event Webhook. This is a tool skill for one vendor (SendGrid). Marketing campaigns, template builders, and other providers are out of scope; this skill owns the operational loop for application-triggered email: send it, check it landed, and verify the events claiming so are authentic.

Operating contract

1. Read-only discovery before any mutation. Check deliverability signals (bounces, spam reports) freely. The bundled email-cli script makes reads without writing anything.
2. Confirm the target, scope, and rollback path before acting. Sending email puts words in recipients' inboxes in your organization's name: it requires an explicit human directive naming the recipients, sender, and content, plus --dry-run preview and --yes confirmation through email-cli. There is no reliable "un-send" for delivered mail.
3. Respect bounded reads. Suppression listings cap results with --limit; never page past what the task needs.
4. Verify webhooks before trusting them. SendGrid's Signed Event Webhook signs every request; verify the ECDSA signature and timestamp before acting on event data. Unverified webhook endpoints accept forged delivery/bounce events.
5. Keep evidence bounded. Quote short message previews and email addresses; never paste API keys, full message bodies, or suppression lists into chat.
6. Never send to unverified addresses or real users without a directive. Deliverability triage reads are safe; the send path is always gated.

The email-cli script

scripts/email-cli is an agent-first, stdlib-only CLI over the SendGrid v3 API, including a self-contained ECDSA P-256 signature verifier with no third-party crypto dependency.