Personalize a message

Write one order-confirmation template, then let every send fill it with that customer’s name, items, and total.

Prerequisites

Personalize the message

Write the template

Put this in an email block in , or create the template in code with the :

Hi {{default profile.first_name "there"}},

{{#each items}}
{{capitalize this.name}}: {{format "$%.2f" this.price}}
{{/each}}

Total: {{format "$%.2f" (add (default subtotal 0) (default tax 0))}}
{{#if placed_at}}Placed {{datetime-format placed_at "%b %d, %Y" profile.timezone}}{{/if}}

Four helpers are doing the work:

Helper	What it handles
`default`	A new customer has no `first_name` yet, so this prints `there` instead of nothing
`each`	Walks the `items` array. Inside the loop, `this` is the current item
`format`	sprintf, so the `$` goes in the format string. There is no currency helper
`add`	Send the parts and let the template add them up, so a change is an edit and not a deploy. Wrap each one in `default`, because `add` on a missing value yields `NaN` and fails the send

datetime-format takes the timestamp, a strftime format, and a timezone. Passing profile.timezone means every customer reads the time in their own zone. Guard it with #if rather than default, since an empty string is not a date either.Anything prefixed with profile. comes from the stored profile. Everything else comes from data on the send.

Send the data it fills in

const { requestId } = await client.send.message({
  message: {
    to: { user_id: 'user_123' },
    template: 'nt_01kx4h2jdafq8bk9aftxak4b40',
    data: {
      placed_at: '2026-05-15T18:30:00Z',
      subtotal: 74.98,
      tax: 6.19,
      items: [
        { name: 'wireless mouse', price: 29.99 },
        { name: 'usb-c hub', price: 44.99 },
      ],
    },
  },
});

response = client.send.message(
    message={
        "to": {"user_id": "user_123"},
        "template": "nt_01kx4h2jdafq8bk9aftxak4b40",
        "data": {
            "placed_at": "2026-05-15T18:30:00Z",
            "subtotal": 74.98,
            "tax": 6.19,
            "items": [
                {"name": "wireless mouse", "price": 29.99},
                {"name": "usb-c hub", "price": 44.99},
            ],
        },
    },
)

curl -X POST https://api.courier.com/send \
  -H "Authorization: Bearer $COURIER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "message": {
      "to": { "user_id": "user_123" },
      "template": "nt_01kx4h2jdafq8bk9aftxak4b40",
      "data": {
        "placed_at": "2026-05-15T18:30:00Z",
        "subtotal": 74.98,
        "tax": 6.19,
        "items": [
          { "name": "wireless mouse", "price": 29.99 },
          { "name": "usb-c hub", "price": 44.99 }
        ]
      }
    }
  }'

response = courier.send_.message(
  message: {
    to: { user_id: "user_123" },
    template: "nt_01kx4h2jdafq8bk9aftxak4b40",
    data: {
      placed_at: "2026-05-15T18:30:00Z",
      subtotal: 74.98,
      tax: 6.19,
      items: [
        { name: "wireless mouse", price: 29.99 },
        { name: "usb-c hub", price: 44.99 }
      ]
    }
  }
)

response, err := client.Send.Message(context.TODO(), courier.SendMessageParams{
	Message: courier.SendMessageParamsMessage{
		To: courier.SendMessageParamsMessageToUnion{
			OfUserRecipient: &shared.UserRecipientParam{
				UserID: courier.String("user_123"),
			},
		},
		Template: courier.String("nt_01kx4h2jdafq8bk9aftxak4b40"),
		Data: map[string]any{
			"placed_at": "2026-05-15T18:30:00Z",
			"subtotal":  74.98,
			"tax":       6.19,
			"items": []any{
				map[string]any{"name": "wireless mouse", "price": 29.99},
				map[string]any{"name": "usb-c hub", "price": 44.99},
			},
		},
	},
})

SendMessageParams params = SendMessageParams.builder()
    .message(SendMessageParams.Message.builder()
        .to(UserRecipient.builder().userId("user_123").build())
        .template("nt_01kx4h2jdafq8bk9aftxak4b40")
        .data(JsonValue.from(java.util.Map.of(
            "placed_at", "2026-05-15T18:30:00Z",
            "subtotal", 74.98,
            "tax", 6.19,
            "items", java.util.List.of(
                java.util.Map.of("name", "wireless mouse", "price", 29.99),
                java.util.Map.of("name", "usb-c hub", "price", 44.99)))))
        .build())
    .build();
SendMessageResponse response = client.send().message(params);

$response = $client->send->message(
  message: [
    'to' => ['user_id' => 'user_123'],
    'template' => 'nt_01kx4h2jdafq8bk9aftxak4b40',
    'data' => [
      'placed_at' => '2026-05-15T18:30:00Z',
      'subtotal' => 74.98,
      'tax' => 6.19,
      'items' => [
        ['name' => 'wireless mouse', 'price' => 29.99],
        ['name' => 'usb-c hub', 'price' => 44.99],
      ],
    ],
  ],
);

SendMessageParams parameters = new()
{
    Message = new()
    {
        To = new UserRecipient { UserID = "user_123" },
        Template = "nt_01kx4h2jdafq8bk9aftxak4b40",
        Data = new Dictionary<string, JsonElement>()
        {
            { "placed_at", JsonSerializer.SerializeToElement("2026-05-15T18:30:00Z") },
            { "subtotal", JsonSerializer.SerializeToElement(74.98) },
            { "tax", JsonSerializer.SerializeToElement(6.19) },
            { "items", JsonSerializer.SerializeToElement(new[]
                {
                    new { name = "wireless mouse", price = 29.99 },
                    new { name = "usb-c hub", price = 44.99 },
                })
            },
        },
    },
};

var response = await client.Send.Message(parameters);

courier send message \
  --api-key "$COURIER_API_KEY" \
  --message.to '{"user_id": "user_123"}' \
  --message.template "nt_01kx4h2jdafq8bk9aftxak4b40" \
  --message.data '{"placed_at": "2026-05-15T18:30:00Z", "subtotal": 74.98, "tax": 6.19, "items": [{"name": "wireless mouse", "price": 29.99}, {"name": "usb-c hub", "price": 44.99}]}'

With Courier MCP, send my nt_01kx4h2jdafq8bk9aftxak4b40 template to user_123 with a wireless mouse and a usb-c hub.

Verify

Read what arrived

Hi Sarah,

Wireless mouse: $29.99
Usb-c hub: $44.99

Total: $81.17
Placed May 15, 2026

Compare it against the data you sent

Open , find the requestId, and read the rendered message next to the data that produced it.

Check the delivered message, not the designer’s preview. The preview substitutes variables but does not run helpers, so format and datetime-format can look wrong there and render correctly when sent.

Handle a missing value

A variable you only print is safe to omit: a missing single-brace variable renders as the literal {tax}, and a missing Handlebars var renders empty. That silence is why the default on the greeting matters. A variable a helper computes with is not safe. Send the template above without tax and add produces NaN, format throws, and the whole message fails with undefined is NaN. The status is UNDELIVERABLE, and nothing is delivered on any channel. The send still returns 202 with a requestId, so the only place this surfaces is the message status. Two helpers in this template need guarding, and they need different guards:

Helper	Missing value	Guard
`add`, and any `format` fed by it	yields `NaN`, then throws	`default` to `0`
`datetime-format`	throws `Cannot read properties of undefined`	`#if` around the line
`each`	renders nothing, safe	none needed

So guard every variable a helper computes with, and reserve the bare form for text you are only printing. That is why the total above is written:

Total: {{format "$%.2f" (add (default subtotal 0) (default tax 0))}}

To fail loudly on the printed kind too, turn on Throw on variable not found in the template’s Advanced settings. It catches a single-brace {tax} left in the rendered output, not a {{tax}} that rendered empty, so the default above is still what protects you. has the full behavior.

Branch on what you know with condition, which takes its operator as a string: {{#if (condition plan "==" "pro")}}Your Pro order ships free.{{/if}}

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Personalize a message

Prerequisites

Personalize the message

Verify

Handle a missing value

​Prerequisites

​Personalize the message

​Verify

​Handle a missing value

Prerequisites

Personalize the message

Verify

Handle a missing value