# Resend > Agent-callable Resend tools — send transactional email, manage contacts and segments, send broadcasts, read delivery status, and diagnose sending domains. Use when the user mentions Resend or wants to send email, manage a contact list, or check email delivery, even if they don't name Resend explicitly. - Skill: `zapier/resend` (Agent Skill, multi-file: 65 files) - Install (CLI): `npx skillmds@latest add zapier/resend` - Raw SKILL.md: https://api.skillmd.com/api/skills/zapier/resend/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - License: Elastic-2.0 - Author: zapier (https://skillmd.com/u/zapier) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/zapier/resend --- # Resend Agent-callable tools for Resend, the email API. Send transactional email to one or more recipients, manage a contact list (create, look up, update, delete contacts and their custom properties), organize contacts into segments and manage segment membership, send a broadcast to an entire segment, read the delivery status of sent email, and check which sending domains are verified. Wraps the public [Resend API](https://resend.com/docs/api-reference/introduction) over a single API-key credential. _Independent, unofficial connector for Resend. Not affiliated with, endorsed by, or sponsored by Resend. "Resend" is a trademark of its owner, used only to identify the service this connector works with._ ## When to use this - **Send email** — a transactional message to specific recipients (`sendEmail`), or a marketing broadcast to a whole segment (`createBroadcast` + `sendBroadcast`). - **Manage contacts** — create, retrieve, update, list, and delete contacts, and read a contact's segments; contacts are addressable by id **or** email address. - **Manage segments** — create, list, get, and delete segments (named groupings a contact can belong to), and add or remove contacts. - **Check delivery and diagnose sends** — read a sent email's status (`getEmail`, `listEmails`), discover custom contact-property keys (`listContactProperties`), verify sending domains (`listDomains`), and trigger a configured automation (`sendEvent`). ## Setup This is an [agentskills.io](https://agentskills.io) skill. If the connector has not been installed as a skill yet, install it first with `npx skills add zapier/connectors --skill resend` (or your harness's own skill-install mechanism), then continue here. Installing the skill copies these files, not dependencies. Before running the CLI, a local MCP server, or `zapier-sdk` auth commands, run `npm install --omit=dev` here once. Importing the published package as a dependency in your own project instead? That `npm install` already resolves everything — see [`references/use-as-sdk.md`](references/use-as-sdk.md). Want the actual repo source instead — to browse `references/`, run this connector's tests, or hack on it? See [`README.md`](README.md#cloning-the-source) for a scoped `git clone`. The connector runs on **Node.js 22.18+**. Pick the reference that matches how you're running it, and load it before doing anything else: | You have... | Load | | ----------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------ | | An MCP-aware client — tools may already be loaded (e.g. `mcp__resend__`), or you can register a local server yourself (or guide the user to) | [`references/use-as-mcp.md`](references/use-as-mcp.md) | | Terminal / subprocess access (you can run `node`) | [`references/use-as-cli.md`](references/use-as-cli.md) | | Only your own code, importing this package as a dependency | [`references/use-as-sdk.md`](references/use-as-sdk.md) | | No tool access, no terminal, no ability to import this package — you write your own code that calls the Resend API directly (e.g. a code-execution sandbox) | [`references/use-as-recipe.md`](references/use-as-recipe.md) | ## Scripts Every script uses the single `resend` connection. Contact-referencing tools accept a contact **id or email address** interchangeably. | Script | Script name | Connections | Description | | ------------------------------------- | -------------------------- | ----------- | ------------------------------------------------------------------------------------------------------ | | `scripts/sendEmail.ts` | `sendEmail` | `resend` | Send a transactional email to one or more recipients. | | `scripts/getEmail.ts` | `getEmail` | `resend` | Retrieve a sent email and its current delivery status. | | `scripts/listEmails.ts` | `listEmails` | `resend` | List previously sent emails, most recent first. | | `scripts/createContact.ts` | `createContact` | `resend` | Create a contact in the account's contact list. | | `scripts/getContact.ts` | `getContact` | `resend` | Retrieve a single contact by id or email. | | `scripts/updateContact.ts` | `updateContact` | `resend` | Update a contact's name, subscription status, or properties. | | `scripts/deleteContact.ts` | `deleteContact` | `resend` | Delete a contact by id or email. | | `scripts/listContacts.ts` | `listContacts` | `resend` | List all contacts in the account. | | `scripts/listContactSegments.ts` | `listContactSegments` | `resend` | List the segments a contact belongs to. | | `scripts/listSegmentContacts.ts` | `listSegmentContacts` | `resend` | List a segment's members. `listContacts` does not filter by segment — use this instead. | | `scripts/createSegment.ts` | `createSegment` | `resend` | Create a named segment. | | `scripts/listSegments.ts` | `listSegments` | `resend` | List the account's segments. | | `scripts/getSegment.ts` | `getSegment` | `resend` | Get a single segment by id. | | `scripts/deleteSegment.ts` | `deleteSegment` | `resend` | Delete a segment (removes the segment, not its contacts — use `deleteContact` for that). | | `scripts/addContactToSegment.ts` | `addContactToSegment` | `resend` | Add a contact to a segment. | | `scripts/removeContactFromSegment.ts` | `removeContactFromSegment` | `resend` | Remove a contact from a segment (changes membership only — use `deleteContact` to remove the contact). | | `scripts/listContactProperties.ts` | `listContactProperties` | `resend` | List the account's custom contact-property keys. | | `scripts/createBroadcast.ts` | `createBroadcast` | `resend` | Draft a broadcast — one email to every contact in a segment. | | `scripts/sendBroadcast.ts` | `sendBroadcast` | `resend` | Send or schedule a previously-created broadcast. | | `scripts/listDomains.ts` | `listDomains` | `resend` | List sending domains and their verification status. | | `scripts/sendEvent.ts` | `sendEvent` | `resend` | Trigger a configured automation by sending a named event. | ## Disambiguation & refusals **Before writing to a segment or contact looked up by name, resolve the id first and count matches.** Segment names and contact names are not unique. When an instruction names a segment (e.g. "add Sarah to the VIP segment") or a person, resolve it via `listSegments` / `listContacts` (or `getContact` by email) and count _exact_ (case-insensitive) matches: - **Exactly one match** → act on it. Don't over-ask for confirmation on an unambiguous single match. - **Two or more that tie on the name** → stop, list the candidates with a distinguishing field (segment `created_at`; contact `email`), and ask which one. Never silently pick the first. **This check still applies even if you already hold a candidate id** — e.g. if you just created two segments with the same name earlier in this session. Already knowing one id is not the same as confirming it's the only match: run `listSegments` / `listContacts` and count matches before writing, the same as if you'd looked the name up fresh. Don't reuse an id from your own recent tool output as a shortcut past the count-and-ask step. Prefer addressing contacts by **email address** when you have it — `getContact`, `updateContact`, `deleteContact`, `addContactToSegment`, `removeContactFromSegment`, and `listContactSegments` all accept an email directly, which sidesteps name collisions entirely. **A successful `updateContact` custom-property write is not proof the value persisted.** Discover valid keys via `listContactProperties` before writing one you haven't already confirmed. If you write a property under a key you haven't verified, read the contact back (`getContact`) before reporting it as set — don't rely on the write call's bare success status alone. **Unsupported operations — say so and stop; don't substitute another tool.** This connector does **not**: - **Verify or provision a sending domain** — `listDomains` is read-only (it reports verification _status_ so you can diagnose a failed send). Adding, verifying, or deleting a domain is DNS work done once in the Resend dashboard; there is no tool for it here. If a send fails because a domain isn't verified, report which domain is unverified and point the user to the dashboard — don't claim to have fixed it. - **Author automations** — `sendEvent` triggers an automation a human already configured in the dashboard; it does not create or edit the automation graph. If asked to build an automation flow, say it's unsupported. - **Manage API keys, webhooks, templates, or suppressions**, or send batch/base64-attachment email. Attachments are supported only by hosted URL (`path`), not raw bytes. ## Auth Every shape passes auth as one connection **selector**, not the secret — a `[:]` string. Every connector accepts `zapier:` (Zapier-managed auth — routes through Zapier's auth, retries, and governance layer); some also accept one or more direct-token resolvers (naming and count vary per connector) — check this connector's own resolvers rather than assuming. The `:` prefix is optional; a bare value goes to the first resolver that claims it — a UUID-shaped bare value always claims `zapier:`. Each script declares the connections it needs and the resolvers each accepts. The exact syntax for passing a connection (and how to see this connector's resolver list) differs by shape — see the reference you loaded above. Checking what's already configured first? Don't dump environment values to do it — `env` or `env | grep ` prints the value along with the name, leaking a live credential into the transcript if one is set. Check names only (`env | cut -d= -f1 | grep -i `) or test a known name directly (`[ -n "$VAR_NAME" ]`). No connection yet? Pick one — and follow the reference's own flow to obtain it; never just ask the user for a connection id or token as if they already have one memorized: | | Load | | ------------------------------------ | ---------------------------------------------------------------------- | | Pass the credential directly | [`references/use-without-zapier.md`](references/use-without-zapier.md) | | Route it through a Zapier connection | [`references/use-with-zapier.md`](references/use-with-zapier.md) | ## Output format Every script returns a `{ data, meta }` envelope: - **`data`** — the script's result (the shape its `outputSchema` declares; see the reference you loaded above for how to inspect a script's exact schema in your shape). - **`meta.outputDataValidation`** — what validating `data` did: - `{ skipped: false, droppedPaths: null }` — validated, nothing removed. - `{ skipped: false, droppedPaths: [...], instruction }` — validated, but those paths were stripped from `data`: fields the script returned from the API that the `outputSchema` doesn't declare. If you need them, re-run with output validation skipped. - `{ skipped: true }` — validation was bypassed; `data` is the raw, unchecked script output. **Reading dropped fields / `skipOutputDataValidation`.** To receive the raw, unvalidated result, opt out of output validation (the exact syntax differs by shape — see the reference you loaded above). Input validation is never skipped. **Trimming the result / `filterOutputData`.** To shrink a large result down to the fields you need, pass a jq expression that post-processes `data` (again, exact syntax per shape). The jq runs against `data` only, NOT the `{ data, meta }` envelope, so write it rooted at `data` (run the script's `--help` — or your shape's equivalent — to see its output schema). The transformed value replaces `data`, `meta` is preserved, and the result is NOT re-validated against the output schema. ## References Load the matching reference file before working in that area: | Reference | Load when | | ---------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | [`references/resend-api-gotchas.md`](references/resend-api-gotchas.md) | Before or after any Resend call — API key permissions, verified-sender/403 rules, rate limits and quotas, the error-code table, `sendEmail` limits (recipients, tags, attachments), `last_event` and domain-status enums, pagination defaults, and broadcast/segment/automation behavior. |