Resend

Resend

Resend is a transactional email API. Domains must be verified before sending. Segments and broadcasts support marketing use cases. Templates provide reusable email layouts. Webhooks deliver real-time delivery notifications.

MCPBundles ops workflows

Broadcast post-send check

1. List broadcasts or fetch one by id for schedule/status — not open/click rates on that GET alone.
2. growth/resend/scripts/pull_emails.py (or make growth-source-resend-refresh) — per-recipient last_event aggregates by subject.
3. Postgres users.email_marketing_opt_out_date since send time — unsub count (webhooks + reconcile may lag).

For campaign sizing before send: list contacts on a segment with summary_only=true for targetable counts.

Tool surface (Pattern A reads)

Read tools accept an optional resource id — omit id to list, pass id for one record. Delete tools take plain UUID params. Callable identities come from list_tools (wire slugs include hash suffixes).

Data Model

• Domains — must pass DNS verification before they may appear in from addresses.
• Emails — outbound message history; list or fetch one by email id.
• Segments — contact lists (Newsletter, bundle:obsidian, etc.); list segments to discover ids.
• Contacts — members of a segment; filter by segment id or segment name; summary_only=true for counts without full rows.
• Broadcasts — bulk marketing sends: configure content and segment, then send or schedule.
• Templates — reusable HTML layouts; must be published before use in Automations.
• Automations — event-triggered drip workflows (configure, list, trigger via custom events). Use {{{RESEND_UNSUBSCRIBE_URL}}} in template HTML.
• Events — custom trigger names for automation entry.
• Webhooks — HTTPS endpoints for sent, delivered, bounced, opened, clicked events.

Gotchas

• From domain must be verified: Sending from @yourdomain.com requires that domain to be verified in Resend.
• Throughput: Marketing and transactional bursts should be paced — queue large mail jobs instead of firing blindly.
• Broadcast metrics: Open/click/bounce rates come from sent-email listing or growth pull scripts — not from broadcast GET alone.
• Broadcast upsert name: Pass name (campaign slug) on create. Content-only updates can omit name; the upsert preserves the existing dashboard name so Resend does not revert to Untitled.
• Broadcast send now: Omit scheduled_at when sending immediately — Resend rejects the literal string "now" as a scheduled time. Use ISO 8601 or in 1 hour only when scheduling ahead.
• Template publishing: Templates start as drafts and must be published before they can be used in emails.
• Webhook verification: Webhook requests include a signing secret returned at creation — use it to verify request authenticity.