Reply to an inbound message

POST

notify

import Prelude from "@prelude.so/sdk";

const client = new Prelude();

async function main() {
  const response = await client.notify.reply({
    to: "+33612345678",
    text: "Thanks for reaching out! We'll look into your request.",
    reply_to: "im_01k8aq2zggeyssvt53zgvpx63a",
  });

  console.log(response.id);
}

main();

package main

import (
	"context"
	"fmt"

	"github.com/prelude-so/go-sdk"
	"github.com/prelude-so/go-sdk/option"
)

func main() {
	client := prelude.NewClient()

	response, err := client.Notify.Reply(context.TODO(), prelude.NotifyReplyParams{
		To:      prelude.F("+33612345678"),
		Text:    prelude.F("Thanks for reaching out! We'll look into your request."),
		ReplyTo: prelude.F("im_01k8aq2zggeyssvt53zgvpx63a"),
	})
	if err != nil {
		panic(err.Error())
	}

	fmt.Printf("%+v\n", response.ID)
}

import os
from prelude_python_sdk import Prelude

client = Prelude()

response = client.notify.reply(
    to="+33612345678",
    text="Thanks for reaching out! We'll look into your request.",
    reply_to="im_01k8aq2zggeyssvt53zgvpx63a",
)

print(response.id)

{
  "id": "tx_01k8ap1btqf5r9fq2c8ax5fhc9",
  "to": "+33612345678",
  "text": "Thanks for reaching out! We'll look into your request.",
  "reply_to": "im_01k8aq2zggeyssvt53zgvpx63a",
  "created_at": "2025-10-24T12:00:00Z",
  "callback_url": "https://your-app.com/webhooks/notify",
  "correlation_id": "support-ticket-42"
}

{
  "code": "invalid_phone_number",
  "message": "The provided phone number is invalid. Provide a valid E.164 phone number.",
  "type": "bad_request",
  "request_id": "3d19215e-2991-4a05-a41a-527314e6ff6a",
  "param": "phone_number"
}

import Prelude from "@prelude.so/sdk";

const client = new Prelude();

async function main() {
  const response = await client.notify.reply({
    to: "+33612345678",
    text: "Thanks for reaching out! We'll look into your request.",
    reply_to: "im_01k8aq2zggeyssvt53zgvpx63a",
  });

  console.log(response.id);
}

main();

package main

import (
	"context"
	"fmt"

	"github.com/prelude-so/go-sdk"
	"github.com/prelude-so/go-sdk/option"
)

func main() {
	client := prelude.NewClient()

	response, err := client.Notify.Reply(context.TODO(), prelude.NotifyReplyParams{
		To:      prelude.F("+33612345678"),
		Text:    prelude.F("Thanks for reaching out! We'll look into your request."),
		ReplyTo: prelude.F("im_01k8aq2zggeyssvt53zgvpx63a"),
	})
	if err != nil {
		panic(err.Error())
	}

	fmt.Printf("%+v\n", response.ID)
}

import os
from prelude_python_sdk import Prelude

client = Prelude()

response = client.notify.reply(
    to="+33612345678",
    text="Thanks for reaching out! We'll look into your request.",
    reply_to="im_01k8aq2zggeyssvt53zgvpx63a",
)

print(response.id)

A reply leaves on the channel the inbound message came in on: a native WhatsApp quoted message, or a plain RCS text from the agent that received the message. It must be sent within the 24-hour conversation window that follows the latest inbound message from the same user. See WhatsApp 2-Way Messaging and RCS 2-Way Messaging for the full flow.

Request fields

string

required

The recipient’s phone number in E.164 format. Must match the phone number that sent the original inbound message, otherwise a phone_number_mismatch error is returned.

string

required

The reply message body. Sent as a free-form text on WhatsApp or RCS, not as a template.

string

required

The inbound message ID (prefixed with im_) to reply to. This ID is provided in the inbound.message.received webhook event.

string

The URL where webhooks will be sent for delivery events of this reply.

string

A user-defined identifier to correlate this reply with your internal systems. It is returned in the response and any webhook events that refer to this message.

Error Handling

The reply endpoint returns specific error codes for 2-way messaging failures:

Error Code	Description	Action
`window_expired`	WhatsApp only: the 24-hour conversation window has closed	Use a template-based message via Send a message instead
`invalid_reply_context`	The inbound message ID in `reply_to` was not found	Verify the message ID from the `inbound.message.received` webhook
`reply_not_supported`	The number or agent that received the message takes no part in 2-way messaging: an OTP agent, or no callback URL is registered	Ask your Customer Success Manager to enable 2-way messaging on that sender
`phone_number_mismatch`	The `to` number does not match the inbound message sender	Use the phone number from the inbound webhook
`missing_text`	The `text` field is empty	Provide a reply message body
`invalid_phone_number`	Phone number format is invalid	Validate phone number format
`insufficient_balance`	Account balance is too low	Top up your account

For a complete list of errors, see the Error documentation.

WhatsApp 2-Way Messaging - Receive inbound WhatsApp messages and send replies
RCS 2-Way Messaging - Receive inbound RCS messages on your agent and send replies
Send a message - Send templated transactional and marketing messages
Webhooks - Receive delivery updates, inbound messages, and subscription events

Authorizations

Authorization

string

header

required

Bearer authentication header of the form Bearer <token>, where <token> is your auth token.

Body

application/json

string

required

The recipient's phone number in E.164 format. Must match the phone number that sent the original inbound message.

Example:

"+33612345678"

text

string

required

The reply message body sent as a free-form WhatsApp text.

Example:

"Thanks for reaching out! We'll look into your request."

reply_to

string

required

The inbound message ID (prefixed with im_) to reply to. This ID is provided in the inbound.message.received webhook event.

Example:

"im_01k8aq2zggeyssvt53zgvpx63a"

callback_url

string

The URL where webhooks will be sent for delivery events of this reply.

Example:

"https://your-app.com/webhooks/notify"

correlation_id

string

A user-defined identifier to correlate this reply with your internal systems. It is returned in the response and any webhook events that refer to this message.

Maximum string length: 80

Example:

"support-ticket-42"

Callbacks

POST

{$request.body#/callback_url}webhook_event

Body

application/json

string

required

The event identifier.

Example:

"evt_01hynf45qvevj844m9az2x2f3c"

created_at

string<date-time>

required

The event creation date.

Example:

"2028-01-01T00:00:00Z"

type

string

required

The event type.

Example:

"<message_type>"

payload

object

required

The event payload.

Show child attributes

Response

Your server accepted the event and will process it.

Response

string

required

The reply message identifier.

Example:

"tx_01k8ap1btqf5r9fq2c8ax5fhc9"

string

required

The recipient's phone number in E.164 format.

Example:

"+33612345678"

text

string

required

The reply message body that was sent.

Example:

"Thanks for reaching out! We'll look into your request."

reply_to

string

required

The inbound message ID this reply was sent in response to.

Example:

"im_01k8aq2zggeyssvt53zgvpx63a"

created_at

string<date-time>

required

The reply creation date in RFC3339 format.

Example:

"2025-10-24T12:00:00Z"

callback_url

string

The callback URL where webhooks will be sent.

Example:

"https://your-app.com/webhooks/notify"

correlation_id

string

The user-defined correlation identifier echoed back from the request.

Maximum string length: 80

Example:

"support-ticket-42"

import Prelude from "@prelude.so/sdk";

const client = new Prelude();

async function main() {
  const response = await client.notify.reply({
    to: "+33612345678",
    text: "Thanks for reaching out! We'll look into your request.",
    reply_to: "im_01k8aq2zggeyssvt53zgvpx63a",
  });

  console.log(response.id);
}

main();

package main

import (
	"context"
	"fmt"

	"github.com/prelude-so/go-sdk"
	"github.com/prelude-so/go-sdk/option"
)

func main() {
	client := prelude.NewClient()

	response, err := client.Notify.Reply(context.TODO(), prelude.NotifyReplyParams{
		To:      prelude.F("+33612345678"),
		Text:    prelude.F("Thanks for reaching out! We'll look into your request."),
		ReplyTo: prelude.F("im_01k8aq2zggeyssvt53zgvpx63a"),
	})
	if err != nil {
		panic(err.Error())
	}

	fmt.Printf("%+v\n", response.ID)
}

import os
from prelude_python_sdk import Prelude

client = Prelude()

response = client.notify.reply(
    to="+33612345678",
    text="Thanks for reaching out! We'll look into your request.",
    reply_to="im_01k8aq2zggeyssvt53zgvpx63a",
)

print(response.id)

{
  "id": "tx_01k8ap1btqf5r9fq2c8ax5fhc9",
  "to": "+33612345678",
  "text": "Thanks for reaching out! We'll look into your request.",
  "reply_to": "im_01k8aq2zggeyssvt53zgvpx63a",
  "created_at": "2025-10-24T12:00:00Z",
  "callback_url": "https://your-app.com/webhooks/notify",
  "correlation_id": "support-ticket-42"
}

{
  "code": "invalid_phone_number",
  "message": "The provided phone number is invalid. Provide a valid E.164 phone number.",
  "type": "bad_request",
  "request_id": "3d19215e-2991-4a05-a41a-527314e6ff6a",
  "param": "phone_number"
}

Documentation

API Reference

Reply to an inbound message

Request fields

Error Handling

Authorizations

Body

Callbacks

Body

Response

Response

​Request fields

​Error Handling

​Related Documentation

Authorizations

Body

Callbacks

Body

Response

Response

Request fields

Error Handling

Related Documentation