> ## Documentation Index > Fetch the complete documentation index at: https://docs.beta.b3os.org/llms.txt > Use this file to discover all available pages before exploring further. # Resend The io.b3os/resend pack: 3 actions with call snippets, fixture outputs, connection setup and error codes, generated from version 1.0.0. `io.b3os/resend` 1.0.0 · `email`, `messaging`, `notifications` · MIT Send transactional email through Resend with your own Resend API key and a domain you verified in Resend: plain text or HTML, cc, bcc and reply-to, idempotent retries with an idempotency key. Also check an email's delivery status and list your sending domains. Every call's result carries `upstream_status` and `timing`: `validate_ms`, `inject_ms`, `render_ms`, `upstream_ms`, `map_ms` and `total_ms`. `upstream` is the service's time; the others are B3OS's own ([call actions](/actions/call)). The snippets below show no timing values, because a fixture records none. ## Connection `resend`, type `bearer`: Resend API key. A Resend API key (re_...) with sending access, from resend.com/api-keys. How to get one: [resend.com](https://resend.com/docs/api-reference/introduction). The credential is sent only to `api.resend.com`. Store the credential once as a [vault connection](/vault) for this pack and key, then name its id in a call's `connections`. Leave the key out and B3OS uses the project's newest connection for the pack and key without a `subject` ([connections](/actions/call#connections)). Hosts it reaches: `api.resend.com`. ## Actions | Action | Effect | MCP tool | Title | |---|---|---|---| | [`send-email`](/actions/catalog/resend#resend-send-email) | irreversible | `resend__send-email` | Send email | | [`get-email`](/actions/catalog/resend#resend-get-email) | read | `resend__get-email` | Get email status | | [`list-domains`](/actions/catalog/resend#resend-list-domains) | read | `resend__list-domains` | List sending domains | send-email **Send email.** Send one email from an address on a domain verified in your Resend account, as HTML, plain text or both. to, cc and bcc take one address or an array. Pass an idempotency key so a retry does not send twice. Returns the Resend email ID. Ref `io.b3os/resend/send-email@1.0.0` · effect `irreversible` · connection `resend` · MCP tool `resend__send-email` **curl** ```bash curl -s https://beta-api.b3os.org/v1/actions/call \ -H "Authorization: Bearer $B3OS_API_KEY" \ -H "Idempotency-Key: 7c1e2f6a-1d43-4a8e-b2a5-3f0c9d5e8b11" \ -H "Content-Type: application/json" \ -d '{ "ref": "io.b3os/resend/send-email@1", "input": { "from": "Acme Billing ", "to": ["ada@example.com"], "subject": "Your October invoice", "text": "Hi Ada, your invoice for October is attached in the portal.", "replyTo": "support@acme.example" }, "connections": {"resend": "conn_01m5t6cbgdjs1ketgcqwa2sne8"} }' ``` **TypeScript** ```ts import { B3OS } from "@b3os/sdk"; const b3os = new B3OS(); const result = await b3os.actions.call({ ref: "io.b3os/resend/send-email@1", input: { from: "Acme Billing ", to: ["ada@example.com"], subject: "Your October invoice", text: "Hi Ada, your invoice for October is attached in the portal.", replyTo: "support@acme.example", }, connections: { resend: "conn_01m5t6cbgdjs1ketgcqwa2sne8" }, }, { idempotencyKey: crypto.randomUUID() }); console.log(result.output); ``` **Python** ```python import uuid from b3os import B3OS b3os = B3OS() result = b3os.actions.call({ "ref": "io.b3os/resend/send-email@1", "input": { "from": "Acme Billing ", "to": ["ada@example.com"], "subject": "Your October invoice", "text": "Hi Ada, your invoice for October is attached in the portal.", "replyTo": "support@acme.example", }, "connections": {"resend": "conn_01m5t6cbgdjs1ketgcqwa2sne8"}, }, idempotency_key=str(uuid.uuid4())) print(result["output"]) ``` **MCP** ```json { "method": "tools/call", "params": { "name": "resend__send-email", "arguments": { "from": "Acme Billing ", "to": ["ada@example.com"], "subject": "Your October invoice", "text": "Hi Ada, your invoice for October is attached in the portal.", "replyTo": "support@acme.example" } } } ``` Expose the pack as tools with `--packs resend` on the local server or `?packs=resend` on the remote URL, and the agent calls `resend__send-email` with the action's input. The tool uses your newest connection for each key without a `subject`. Without exposing the pack, `actions_call` takes the same input with `ref`. Output, labeled `fixture`: Send email (documented response shape, example values). From the bundle's `fixtures/send-email.json`, not a live call. ```json {"id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794", "status": "success"} ``` When the service answers with an error, the call fails with [`upstream_error`](/errors#upstream_error) and `pack_error.code` is one of: | `pack_error.code` | Service status | Retryable | Message | |---|---|---|---| | `connection_unauthorized` | 401 | no | Resend rejected the API key; check the connection. | | `forbidden` | 403 | no | built from the service's response | | `not_found` | 404 | no | built from the service's response | | `rate_limited` | 429 | yes | built from the service's response | | `invalid_request` | 400, 422 | no | built from the service's response | | `conflict` | 409 | no | built from the service's response | get-email **Get email status.** One sent email by Resend ID: sender, recipients, subject, creation time and its last delivery event (sent, delivered, delivery_delayed, bounced, complained, opened, clicked, ...). Ref `io.b3os/resend/get-email@1.0.0` · effect `read` · connection `resend` · MCP tool `resend__get-email` **curl** ```bash curl -s https://beta-api.b3os.org/v1/actions/call \ -H "Authorization: Bearer $B3OS_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "ref": "io.b3os/resend/get-email@1", "input": {"id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794"}, "connections": {"resend": "conn_01m5t6cbgdjs1ketgcqwa2sne8"} }' ``` **TypeScript** ```ts import { B3OS } from "@b3os/sdk"; const b3os = new B3OS(); const result = await b3os.actions.call({ ref: "io.b3os/resend/get-email@1", input: { id: "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794" }, connections: { resend: "conn_01m5t6cbgdjs1ketgcqwa2sne8" }, }); console.log(result.output); ``` **Python** ```python from b3os import B3OS b3os = B3OS() result = b3os.actions.call({ "ref": "io.b3os/resend/get-email@1", "input": {"id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794"}, "connections": {"resend": "conn_01m5t6cbgdjs1ketgcqwa2sne8"}, }) print(result["output"]) ``` **MCP** ```json { "method": "tools/call", "params": { "name": "resend__get-email", "arguments": {"id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794"} } } ``` Expose the pack as tools with `--packs resend` on the local server or `?packs=resend` on the remote URL, and the agent calls `resend__get-email` with the action's input. The tool uses your newest connection for each key without a `subject`. Without exposing the pack, `actions_call` takes the same input with `ref`. Output, labeled `fixture`: Get email status (documented response shape, example values). From the bundle's `fixtures/get-email.json`, not a live call. ```json { "id": "49a3999c-0ce1-4ea6-ab68-afcd6dc2e794", "from": "Acme Billing ", "to": ["ada@example.com"], "subject": "Your October invoice", "created_at": "2026-10-26 09:12:44.123456+00", "last_event": "delivered" } ``` When the service answers with an error, the call fails with [`upstream_error`](/errors#upstream_error) and `pack_error.code` is one of: | `pack_error.code` | Service status | Retryable | Message | |---|---|---|---| | `connection_unauthorized` | 401 | no | Resend rejected the API key; check the connection. | | `forbidden` | 403 | no | built from the service's response | | `not_found` | 404 | no | built from the service's response | | `rate_limited` | 429 | yes | built from the service's response | | `invalid_request` | 400, 422 | no | built from the service's response | | `conflict` | 409 | no | built from the service's response | list-domains **List sending domains.** Domains in the Resend account with their verification status (verified, pending, failed, ...) and region. send-email only works from verified domains. Ref `io.b3os/resend/list-domains@1.0.0` · effect `read` · connection `resend` · MCP tool `resend__list-domains` **curl** ```bash curl -s https://beta-api.b3os.org/v1/actions/call \ -H "Authorization: Bearer $B3OS_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "ref": "io.b3os/resend/list-domains@1", "input": {}, "connections": {"resend": "conn_01m5t6cbgdjs1ketgcqwa2sne8"} }' ``` **TypeScript** ```ts import { B3OS } from "@b3os/sdk"; const b3os = new B3OS(); const result = await b3os.actions.call({ ref: "io.b3os/resend/list-domains@1", input: {}, connections: { resend: "conn_01m5t6cbgdjs1ketgcqwa2sne8" }, }); console.log(result.output); ``` **Python** ```python from b3os import B3OS b3os = B3OS() result = b3os.actions.call({ "ref": "io.b3os/resend/list-domains@1", "input": {}, "connections": {"resend": "conn_01m5t6cbgdjs1ketgcqwa2sne8"}, }) print(result["output"]) ``` **MCP** ```json { "method": "tools/call", "params": {"name": "resend__list-domains", "arguments": {}} } ``` Expose the pack as tools with `--packs resend` on the local server or `?packs=resend` on the remote URL, and the agent calls `resend__list-domains` with the action's input. The tool uses your newest connection for each key without a `subject`. Without exposing the pack, `actions_call` takes the same input with `ref`. Output, labeled `fixture`: List sending domains (documented response shape, example values). From the bundle's `fixtures/list-domains.json`, not a live call. ```json { "domains": [ { "id": "d91cd9bd-1176-453e-8fc1-35364d380206", "name": "acme.example", "status": "verified", "region": "us-east-1", "created_at": "2026-04-26 20:21:26.347412+00" }, { "id": "1c7b4b2a-6a51-4b5e-9a35-1f0f2b5d7c11", "name": "mail.acme.example", "status": "pending", "region": "eu-west-1", "created_at": "2026-10-20 10:02:11.000000+00" } ] } ``` When the service answers with an error, the call fails with [`upstream_error`](/errors#upstream_error) and `pack_error.code` is one of: | `pack_error.code` | Service status | Retryable | Message | |---|---|---|---| | `connection_unauthorized` | 401 | no | Resend rejected the API key; check the connection. | | `forbidden` | 403 | no | built from the service's response | | `not_found` | 404 | no | built from the service's response | | `rate_limited` | 429 | yes | built from the service's response | | `invalid_request` | 400, 422 | no | built from the service's response | | `conflict` | 409 | no | built from the service's response |