Send16 MCP Server

Add a single new contact, optionally straight into audiences and/or with tags; e.g. 'add this person from my email into the newsletter list'. Contacts are subscribed by default. For more than a handful of people, use import_contacts instead.

Delete a contact and all associated events. Irreversible.

Get a contact's 0-100 health score based on recent engagement (opens, clicks, replies).

Get a contact's full activity timeline: emails received, events fired, opens, clicks, automation enrollments, topic changes.

Remove a contact from an audience.

Update a contact's profile fields, custom fields, or subscription state.

One-shot broadcast: create a campaign and immediately schedule it to send, in a single call. Pass either an audienceId, segmentId, topicId, or fully-qualified filter. Provide html OR templateSlug. Before calling, confirm with the user: show them the recipients (or the recipient count), the sender and the subject, and wait for a clear yes. Send16 can refuse a send. 429 SEND_RAMP_LIMIT: new and free workspaces have hourly and daily sending limits while they build reputation; the error details give the window, the limit and how many remain. Tell the user how many can go now and that the rest can go once the window resets (or after upgrading), and do not split the send or retry in a loop to get around it. 403 SENDING_PAUSED: sending from the workspace is paused while the Send16 team reviews it. Nothing was sent. Tell the user to check the workspace owner's email or contact support, and do not retry. 422 MESSAGE_NEEDS_REVIEW: the content looked like it might be impersonating a government agency, bank, toll operator or delivery company, so it was held and not sent. Tell the user it is held for review and they can contact support if it is legitimate. Do not reword it and try again; repeated flags pause the workspace.

Send a test email for an existing campaign to preview how it will look in recipients' inboxes. Confirm the test address with the user first. Can be refused with 403 SENDING_PAUSED (workspace under review, nothing was sent, tell the user to contact support).

Send a transactional email through Send16. Provide `html`, `text`, or both (text-only is fine for OTPs/receipts/alerts). `from_email` must belong to a domain that is verified in the workspace; call `whoami` for the account and `list_domains` to see which senders are allowed; a send from an unverified domain returns a clear error, not a silent failure. For a zero-setup first send, use from_email `[email protected]`; the sandbox sender delivers with no DNS, but only to your own account email. Before calling, confirm with the user: show them the recipients (or the recipient count), the sender and the subject, and wait for a clear yes. Send16 can refuse a send. 429 SEND_RAMP_LIMIT: new and free workspaces have hourly and daily sending limits while they build reputation; the error details give the window, the limit and how many remain. Tell the user how many can go now and that the rest can go once the window resets (or after upgrading), and do not split the send or retry in a loop to get around it. 403 SENDING_PAUSED: sending from the workspace is paused while the Send16 team reviews it. Nothing was sent. Tell the user to check the workspace owner's email or contact support, and do not retry. 422 MESSAGE_NEEDS_REVIEW: the content looked like it might be impersonating a government agency, bank, toll operator or delivery company, so it was held and not sent. Tell the user it is held for review and they can contact support if it is legitimate. Do not reword it and try again; repeated flags pause the workspace.

Fire a custom event for a contact. Automations whose trigger is `{type:'custom_event', eventName:'<name>'}` will enroll the contact and start running. Payload is exposed to condition steps as `event.<key>`. Confirm with the user first if the event could start an automation that emails the contact.

Reply to an inbox conversation. The reply is sent from the original recipient address (the alias the convo arrived on) and threaded back to the contact. Show the user the reply text and get a clear yes first: it goes to a real person and cannot be unsent. Can be refused with 403 SENDING_PAUSED (workspace under review, nothing was sent, tell the user to contact support).

Send a preview of a saved workspace template to one email address, so the user can see it in a real inbox. It arrives from [email protected] with a small 'Template test preview' banner and uses sample merge values (first name 'Test'). Only send to the user's own address unless they ask otherwise. Confirm the test address with the user first. Can be refused with 403 SENDING_PAUSED (workspace under review, nothing was sent, tell the user to contact support).

Create an Action that maps an event name to a transactional template. Each matching event sends one email to the contact.

Delete an Action.

Get a single Action with its trigger config and template binding.

Update an Action (toggle enabled, change template, change event name).

Create a new email campaign as a draft: optionally with full HTML content and recipients (exactly ONE of audienceIds / segmentId / contactIds / tagIds / sendToAll) so it's ready to test and send. Nothing is sent until schedule_campaign.

Delete a draft campaign. Sent campaigns cannot be deleted (only archived).

Get detailed performance statistics for a specific campaign including open rate, click rate, bounce rate, and delivery metrics.

Update a draft campaign: name, subject, preview text, sender info, HTML content, and/or recipients. Retarget with exactly ONE of audienceIds / segmentId / contactIds / tagIds / sendToAll, then verify with preview_campaign_recipients before sending. Only drafts can be edited.

Get a single automation by ID, including its trigger, steps, and current status.

Get aggregate analytics for an automation: total enrollments, completed, exited, open/click rates per step.

List active and historical enrollments for an automation.

Add contacts (by ID) to an audience.

List all contacts with optional filtering by subscription status and tag. Supports pagination.

Search contacts by email address or name. Returns matching contacts with their tags and subscription status.

Add a private internal note on a conversation. Notes are visible only to workspace members.

Get a single conversation with its full thread of posts (incoming + outgoing).

Update conversation status (open/closed/archived/snoozed) or assignee.

Create a new subscription topic. Contacts opt into topics individually via the preference center.

Delete a subscription topic. All subscribers will be detached.

Update a subscription topic (name, description, default).

Get the current workspace (the one the API key belongs to).

Get the current month's send count, contact count, and plan limits.

List the templates saved in the user's own Send16 workspace (their template library, including ones saved with save_template). For the shared starter gallery use list_templates.

Create a new audience.

Delete an audience (list). Contacts are not deleted; only the list and its memberships are removed.

Get the workspace's brand settings: colors, logo, fonts, and the DESIGN.md spec injected into AI generation prompts.

Update workspace brand settings. The designSpec field is a Markdown DESIGN.md document fed into AI generation system prompts; use it to encode voice, do/don't lists, and visual rules. companyName/websiteUrl/companyAddress also fill the matching merge tags in templates.

Register a new sending domain. Returns the DNS records the user must add to their DNS provider, after which they should call check_domain_health to verify.

Check the DNS health of a specific domain, including DKIM, SPF, DMARC, and MX record verification status. Triggers a fresh DNS lookup.

Who registered and who came for one event: counts, no-show rate, where people came from (city and state), first-timers vs returning, organisations and registrations over time. Without an eventId, returns insights across every event: regulars and their attendance streaks, cohort retention and the regions growing fastest.

List the people registered for an event, with status (registered, waitlisted, attended, no_show, cancelled), company, city and check-in time.

Fetch a single message with its full event timeline (created → sent → delivered → opened → clicked → ...).

Get just the delivery event timeline for a message: no body or recipient details.

Pause an automation. Existing enrollments freeze in place; no new contacts enroll.

Pause a sending campaign. Already-sent messages are unaffected; remaining sends halt.

Preview the recipient set for a campaign before sending. Returns count + sample list.

Preview the contacts that match a segment without sending.

Add an email to the suppression list. Future sends to this address will be blocked.

Remove an email from the suppression list. Use only when you've confirmed the recipient wants to receive mail again.

Register an outgoing webhook endpoint. Send16 POSTs event JSON to this URL with an HMAC-SHA256 signature. Outgoing webhooks are a plan feature.

Delete an outgoing webhook endpoint.

List Actions. Actions fire a transactional template when a custom event arrives: simple 'event_name → template' pairings, lighter than full automations.

Activate an automation. New events matching its triggers will start enrolling contacts. Confirm with the user first: once active it can start emailing contacts straight away.

Check a registrant in at the door (or undo it). Use the registration ID from list_event_registrations.

List audiences (lists). An audience is a static, manually-managed group of contacts.

List all automations in the workspace, including draft/active/paused status and trigger types.

List email campaigns, newest first. Use `search` to find a past campaign the user describes vaguely ('the invite one', 'that July newsletter'); it matches name and subject case-insensitively; try distinctive words from their description and broaden if no hits.

List inbox conversations. Filter by state, mailbox, label, screener status, or full-text search. Send16's unified inbox combines transactional reply threading with team-managed shared inboxes.

Get your workspace's deliverability summary: sending reputation, domain authentication status, and recent bounce/complaint health. (Deliverability Hub plan feature.)

Use AI to generate a complete email HTML template based on a description. Returns ready-to-use HTML that can be sent or used in campaigns.

List all sending domains configured in your Send16 workspace, including their verification status and DNS records.

Duplicate a campaign (template, content, and settings) as a new draft; works on sent campaigns too, so this is the way to re-use a past campaign's design. Optionally rename and retarget in the same call (exactly ONE of audienceIds / segmentId / contactIds / tagIds / sendToAll). NOTE: without retargeting, the copy keeps the ORIGINAL campaign's recipients.

Manually enroll a contact in an active automation. The automation must be in 'active' status. Use send_event for event-driven enrollment. Confirm with the user first: the automation can start emailing the contact straight away.

List the workspace's events (meetups, workshops, conferences) with registered, attended and no-show counts and each event's public registration page.

Scrape a URL (e.g. a launch blog post or product page) and generate an email draft from its content. Returns subject, preview text, and HTML body.

Bulk import contacts from CSV data (min column: email), optionally straight into audiences and/or with tags. This is the tool for cross-app flows; e.g. pulling people out of Gmail, a CRM, or a spreadsheet and landing them in a Send16 audience in one call. Set updateExisting for upsert semantics (safe to re-run). Requires consentConfirmed: true, so confirm with the user that everyone on the list opted in before calling.

Get unread/total counts per category and label for the inbox sidebar (newsletter, transactional, marketing, calendar, social, cold).

Mark a conversation as read for the current viewer.

List messages from the unified send log (transactional + campaign). Filter by recipient, sender, status, date range, or source.

Run an AI pre-send review on an email's HTML before sending. Surfaces tone issues, broken links, missing alt text, spam triggers, and accessibility problems.

Rotate the HMAC signing secret for an outgoing webhook endpoint. Returns the new secret once.

Register someone for an event. They get the event's confirmation email with their QR ticket unless the organiser switched it off, so confirm the person and the event with the user first. Registering doesn't subscribe them to marketing unless marketingOptIn is true because they asked.

Compile an EmailContent JSON object (the shape used by the Send16 builder + templates) into HTML using the platform's authoritative renderer. Returns the exact HTML the API would send. Useful for previews and post-processing.

Resume a paused campaign. Confirm with the user first: the remaining recipients start receiving the campaign straight away. The sending limits and pauses described on schedule_campaign still apply.

Save an email design as a reusable template in the user's Send16 workspace. Use this when the user has designed an email (for example in a Claude artifact) and wants it in Send16. Pass the complete email HTML. Send16 hosts every image (remote URLs and inline data: images), converts merge tags like {{first_name}} to Send16's format, and stores the HTML exactly as designed. For best results across Gmail, Outlook and Apple Mail the HTML should be email-safe: table-based layout around 600px wide, inline styles, PNG/JPG/GIF images in <img> tags (not SVG or CSS backgrounds), web-safe font fallbacks, and alt text on images. Returns the template id; follow up with send_template_test to send a preview.

Schedule (or send immediately) an existing draft campaign to an audience/segment/topic. Before calling, confirm with the user: show them the recipients (or the recipient count), the sender and the subject, and wait for a clear yes. Send16 can refuse a send. 429 SEND_RAMP_LIMIT: new and free workspaces have hourly and daily sending limits while they build reputation; the error details give the window, the limit and how many remain. Tell the user how many can go now and that the rest can go once the window resets (or after upgrading), and do not split the send or retry in a loop to get around it. 403 SENDING_PAUSED: sending from the workspace is paused while the Send16 team reviews it. Nothing was sent. Tell the user to check the workspace owner's email or contact support, and do not retry. 422 MESSAGE_NEEDS_REVIEW: the content looked like it might be impersonating a government agency, bank, toll operator or delivery company, so it was held and not sent. Tell the user it is held for review and they can contact support if it is legitimate. Do not reword it and try again; repeated flags pause the workspace.

Decide a pending screener conversation (first-time sender). 'allow' lets future emails through, 'reject' blocks, 'cold' marks as cold outreach.

List dynamic segments. Segments compute their members from a filter expression at send time.

List suppressed email addresses (bounces, complaints, unsubscribes, manual).

Get a single starter template by ID, including its EmailContent JSON.

List starter-gallery email templates available to every workspace.

List subscription topics. Topics are granular categories contacts can subscribe to (e.g. 'product-updates', 'weekly-digest'). Campaigns and automations can be gated to subscribers of a specific topic.

List configured outgoing webhooks (your endpoints that Send16 POSTs delivery events to). Outgoing webhooks are a plan feature.

Verify the API key and return the authenticated workspace: name, plan, email quota (used/limit), and owner. Call this first to confirm the key works before sending. Pair with list_domains to see which `from` addresses are allowed.

List workspaces the authenticated user has access to (owner or member).